source: MondoRescue/branches/3.3/mindi-busybox/shell/hush.c@ 3621

/* vi: set sw=4 ts=4: */
/*
 * A prototype Bourne shell grammar parser.
 * Intended to follow the original Thompson and Ritchie
 * "small and simple is beautiful" philosophy, which
 * incidentally is a good match to today's BusyBox.
 *
 * Copyright (C) 2000,2001  Larry Doolittle <larry@doolittle.boa.org>
 * Copyright (C) 2008,2009  Denys Vlasenko <vda.linux@googlemail.com>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 *
 * Credits:
 *      The parser routines proper are all original material, first
 *      written Dec 2000 and Jan 2001 by Larry Doolittle.  The
 *      execution engine, the builtins, and much of the underlying
 *      support has been adapted from busybox-0.49pre's lash, which is
 *      Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
 *      written by Erik Andersen <andersen@codepoet.org>.  That, in turn,
 *      is based in part on ladsh.c, by Michael K. Johnson and Erik W.
 *      Troan, which they placed in the public domain.  I don't know
 *      how much of the Johnson/Troan code has survived the repeated
 *      rewrites.
 *
 * Other credits:
 *      o_addchr derived from similar w_addchar function in glibc-2.2.
 *      parse_redirect, redirect_opt_num, and big chunks of main
 *      and many builtins derived from contributions by Erik Andersen.
 *      Miscellaneous bugfixes from Matt Kraai.
 *
 * There are two big (and related) architecture differences between
 * this parser and the lash parser.  One is that this version is
 * actually designed from the ground up to understand nearly all
 * of the Bourne grammar.  The second, consequential change is that
 * the parser and input reader have been turned inside out.  Now,
 * the parser is in control, and asks for input as needed.  The old
 * way had the input reader in control, and it asked for parsing to
 * take place as needed.  The new way makes it much easier to properly
 * handle the recursion implicit in the various substitutions, especially
 * across continuation lines.
 *
 * TODOs:
 *      grep for "TODO" and fix (some of them are easy)
 *      special variables (done: PWD, PPID, RANDOM)
 *      tilde expansion
 *      aliases
 *      follow IFS rules more precisely, including update semantics
 *      builtins mandated by standards we don't support:
 *          [un]alias, command, fc, getopts, newgrp, readonly, times
 *      make complex ${var%...} constructs support optional
 *      make here documents optional
 *
 * Bash compat TODO:
 *      redirection of stdout+stderr: &> and >&
 *      reserved words: function select
 *      advanced test: [[ ]]
 *      process substitution: <(list) and >(list)
 *      =~: regex operator
 *      let EXPR [EXPR...]
 *          Each EXPR is an arithmetic expression (ARITHMETIC EVALUATION)
 *          If the last arg evaluates to 0, let returns 1; 0 otherwise.
 *          NB: let `echo 'a=a + 1'` - error (IOW: multi-word expansion is used)
 *      ((EXPR))
 *          The EXPR is evaluated according to ARITHMETIC EVALUATION.
 *          This is exactly equivalent to let "EXPR".
 *      $[EXPR]: synonym for $((EXPR))
 *
 * Won't do:
 *      In bash, export builtin is special, its arguments are assignments
 *          and therefore expansion of them should be "one-word" expansion:
 *              $ export i=`echo 'a  b'` # export has one arg: "i=a  b"
 *          compare with:
 *              $ ls i=`echo 'a  b'`     # ls has two args: "i=a" and "b"
 *              ls: cannot access i=a: No such file or directory
 *              ls: cannot access b: No such file or directory
 *          Note1: same applies to local builtin.
 *          Note2: bash 3.2.33(1) does this only if export word itself
 *          is not quoted:
 *              $ export i=`echo 'aaa  bbb'`; echo "$i"
 *              aaa  bbb
 *              $ "export" i=`echo 'aaa  bbb'`; echo "$i"
 *              aaa
 */
#if !(defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__NetBSD__) \
    || defined(__APPLE__) \
    )
# include <malloc.h>   /* for malloc_trim */
#endif
#include <glob.h>
/* #include <dmalloc.h> */
#if ENABLE_HUSH_CASE
# include <fnmatch.h>
#endif
#include <sys/utsname.h> /* for setting $HOSTNAME */

#include "busybox.h"  /* for APPLET_IS_NOFORK/NOEXEC */
#include "unicode.h"
#include "shell_common.h"
#include "math.h"
#include "match.h"
#if ENABLE_HUSH_RANDOM_SUPPORT
# include "random.h"
#else
# define CLEAR_RANDOM_T(rnd) ((void)0)
#endif
#ifndef PIPE_BUF
# define PIPE_BUF 4096  /* amount of buffering in a pipe */
#endif

//config:config HUSH
//config:   bool "hush"
//config:   default y
//config:   help
//config:     hush is a small shell (25k). It handles the normal flow control
//config:     constructs such as if/then/elif/else/fi, for/in/do/done, while loops,
//config:     case/esac. Redirections, here documents, $((arithmetic))
//config:     and functions are supported.
//config:
//config:     It will compile and work on no-mmu systems.
//config:
//config:     It does not handle select, aliases, tilde expansion,
//config:     &>file and >&file redirection of stdout+stderr.
//config:
//config:config HUSH_BASH_COMPAT
//config:   bool "bash-compatible extensions"
//config:   default y
//config:   depends on HUSH
//config:   help
//config:     Enable bash-compatible extensions.
//config:
//config:config HUSH_BRACE_EXPANSION
//config:   bool "Brace expansion"
//config:   default y
//config:   depends on HUSH_BASH_COMPAT
//config:   help
//config:     Enable {abc,def} extension.
//config:
//config:config HUSH_HELP
//config:   bool "help builtin"
//config:   default y
//config:   depends on HUSH
//config:   help
//config:     Enable help builtin in hush. Code size + ~1 kbyte.
//config:
//config:config HUSH_INTERACTIVE
//config:   bool "Interactive mode"
//config:   default y
//config:   depends on HUSH
//config:   help
//config:     Enable interactive mode (prompt and command editing).
//config:     Without this, hush simply reads and executes commands
//config:     from stdin just like a shell script from a file.
//config:     No prompt, no PS1/PS2 magic shell variables.
//config:
//config:config HUSH_SAVEHISTORY
//config:   bool "Save command history to .hush_history"
//config:   default y
//config:   depends on HUSH_INTERACTIVE && FEATURE_EDITING_SAVEHISTORY
//config:   help
//config:     Enable history saving in hush.
//config:
//config:config HUSH_JOB
//config:   bool "Job control"
//config:   default y
//config:   depends on HUSH_INTERACTIVE
//config:   help
//config:     Enable job control: Ctrl-Z backgrounds, Ctrl-C interrupts current
//config:     command (not entire shell), fg/bg builtins work. Without this option,
//config:     "cmd &" still works by simply spawning a process and immediately
//config:     prompting for next command (or executing next command in a script),
//config:     but no separate process group is formed.
//config:
//config:config HUSH_TICK
//config:   bool "Process substitution"
//config:   default y
//config:   depends on HUSH
//config:   help
//config:     Enable process substitution `command` and $(command) in hush.
//config:
//config:config HUSH_IF
//config:   bool "Support if/then/elif/else/fi"
//config:   default y
//config:   depends on HUSH
//config:   help
//config:     Enable if/then/elif/else/fi in hush.
//config:
//config:config HUSH_LOOPS
//config:   bool "Support for, while and until loops"
//config:   default y
//config:   depends on HUSH
//config:   help
//config:     Enable for, while and until loops in hush.
//config:
//config:config HUSH_CASE
//config:   bool "Support case ... esac statement"
//config:   default y
//config:   depends on HUSH
//config:   help
//config:     Enable case ... esac statement in hush. +400 bytes.
//config:
//config:config HUSH_FUNCTIONS
//config:   bool "Support funcname() { commands; } syntax"
//config:   default y
//config:   depends on HUSH
//config:   help
//config:     Enable support for shell functions in hush. +800 bytes.
//config:
//config:config HUSH_LOCAL
//config:   bool "Support local builtin"
//config:   default y
//config:   depends on HUSH_FUNCTIONS
//config:   help
//config:     Enable support for local variables in functions.
//config:
//config:config HUSH_RANDOM_SUPPORT
//config:   bool "Pseudorandom generator and $RANDOM variable"
//config:   default y
//config:   depends on HUSH
//config:   help
//config:     Enable pseudorandom generator and dynamic variable "$RANDOM".
//config:     Each read of "$RANDOM" will generate a new pseudorandom value.
//config:
//config:config HUSH_EXPORT_N
//config:   bool "Support 'export -n' option"
//config:   default y
//config:   depends on HUSH
//config:   help
//config:     export -n unexports variables. It is a bash extension.
//config:
//config:config HUSH_MODE_X
//config:   bool "Support 'hush -x' option and 'set -x' command"
//config:   default y
//config:   depends on HUSH
//config:   help
//config:     This instructs hush to print commands before execution.
//config:     Adds ~300 bytes.
//config:
//config:config MSH
//config:   bool "msh (deprecated: aliased to hush)"
//config:   default n
//config:   select HUSH
//config:   help
//config:     msh is deprecated and will be removed, please migrate to hush.
//config:

//applet:IF_HUSH(APPLET(hush, BB_DIR_BIN, BB_SUID_DROP))
//applet:IF_MSH(APPLET(msh, BB_DIR_BIN, BB_SUID_DROP))
//applet:IF_FEATURE_SH_IS_HUSH(APPLET_ODDNAME(sh, hush, BB_DIR_BIN, BB_SUID_DROP, sh))
//applet:IF_FEATURE_BASH_IS_HUSH(APPLET_ODDNAME(bash, hush, BB_DIR_BIN, BB_SUID_DROP, bash))

//kbuild:lib-$(CONFIG_HUSH) += hush.o match.o shell_common.o
//kbuild:lib-$(CONFIG_HUSH_RANDOM_SUPPORT) += random.o

/* -i (interactive) and -s (read stdin) are also accepted,
 * but currently do nothing, therefore aren't shown in help.
 * NOMMU-specific options are not meant to be used by users,
 * therefore we don't show them either.
 */
//usage:#define hush_trivial_usage
//usage:    "[-nxl] [-c 'SCRIPT' [ARG0 [ARGS]] / FILE [ARGS]]"
//usage:#define hush_full_usage "\n\n"
//usage:    "Unix shell interpreter"

//usage:#define msh_trivial_usage hush_trivial_usage
//usage:#define msh_full_usage hush_full_usage

//usage:#if ENABLE_FEATURE_SH_IS_HUSH
//usage:# define sh_trivial_usage hush_trivial_usage
//usage:# define sh_full_usage    hush_full_usage
//usage:#endif
//usage:#if ENABLE_FEATURE_BASH_IS_HUSH
//usage:# define bash_trivial_usage hush_trivial_usage
//usage:# define bash_full_usage    hush_full_usage
//usage:#endif


/* Build knobs */
#define LEAK_HUNTING 0
#define BUILD_AS_NOMMU 0
/* Enable/disable sanity checks. Ok to enable in production,
 * only adds a bit of bloat. Set to >1 to get non-production level verbosity.
 * Keeping 1 for now even in released versions.
 */
#define HUSH_DEBUG 1
/* Slightly bigger (+200 bytes), but faster hush.
 * So far it only enables a trick with counting SIGCHLDs and forks,
 * which allows us to do fewer waitpid's.
 * (we can detect a case where neither forks were done nor SIGCHLDs happened
 * and therefore waitpid will return the same result as last time)
 */
#define ENABLE_HUSH_FAST 0
/* TODO: implement simplified code for users which do not need ${var%...} ops
 * So far ${var%...} ops are always enabled:
 */
#define ENABLE_HUSH_DOLLAR_OPS 1


#if BUILD_AS_NOMMU
# undef BB_MMU
# undef USE_FOR_NOMMU
# undef USE_FOR_MMU
# define BB_MMU 0
# define USE_FOR_NOMMU(...) __VA_ARGS__
# define USE_FOR_MMU(...)
#endif

#include "NUM_APPLETS.h"
#if NUM_APPLETS == 1
/* STANDALONE does not make sense, and won't compile */
# undef CONFIG_FEATURE_SH_STANDALONE
# undef ENABLE_FEATURE_SH_STANDALONE
# undef IF_FEATURE_SH_STANDALONE
# undef IF_NOT_FEATURE_SH_STANDALONE
# define ENABLE_FEATURE_SH_STANDALONE 0
# define IF_FEATURE_SH_STANDALONE(...)
# define IF_NOT_FEATURE_SH_STANDALONE(...) __VA_ARGS__
#endif

#if !ENABLE_HUSH_INTERACTIVE
# undef ENABLE_FEATURE_EDITING
# define ENABLE_FEATURE_EDITING 0
# undef ENABLE_FEATURE_EDITING_FANCY_PROMPT
# define ENABLE_FEATURE_EDITING_FANCY_PROMPT 0
# undef ENABLE_FEATURE_EDITING_SAVE_ON_EXIT
# define ENABLE_FEATURE_EDITING_SAVE_ON_EXIT 0
#endif

/* Do we support ANY keywords? */
#if ENABLE_HUSH_IF || ENABLE_HUSH_LOOPS || ENABLE_HUSH_CASE
# define HAS_KEYWORDS 1
# define IF_HAS_KEYWORDS(...) __VA_ARGS__
# define IF_HAS_NO_KEYWORDS(...)
#else
# define HAS_KEYWORDS 0
# define IF_HAS_KEYWORDS(...)
# define IF_HAS_NO_KEYWORDS(...) __VA_ARGS__
#endif

/* If you comment out one of these below, it will be #defined later
 * to perform debug printfs to stderr: */
#define debug_printf(...)        do {} while (0)
/* Finer-grained debug switches */
#define debug_printf_parse(...)  do {} while (0)
#define debug_print_tree(a, b)   do {} while (0)
#define debug_printf_exec(...)   do {} while (0)
#define debug_printf_env(...)    do {} while (0)
#define debug_printf_jobs(...)   do {} while (0)
#define debug_printf_expand(...) do {} while (0)
#define debug_printf_varexp(...) do {} while (0)
#define debug_printf_glob(...)   do {} while (0)
#define debug_printf_list(...)   do {} while (0)
#define debug_printf_subst(...)  do {} while (0)
#define debug_printf_clean(...)  do {} while (0)

#define ERR_PTR ((void*)(long)1)

#define JOB_STATUS_FORMAT    "[%d] %-22s %.40s\n"

#define _SPECIAL_VARS_STR     "_*@$!?#"
#define SPECIAL_VARS_STR     ("_*@$!?#" + 1)
#define NUMERIC_SPECVARS_STR ("_*@$!?#" + 3)
#if ENABLE_HUSH_BASH_COMPAT
/* Support / and // replace ops */
/* Note that // is stored as \ in "encoded" string representation */
# define VAR_ENCODED_SUBST_OPS      "\\/%#:-=+?"
# define VAR_SUBST_OPS             ("\\/%#:-=+?" + 1)
# define MINUS_PLUS_EQUAL_QUESTION ("\\/%#:-=+?" + 5)
#else
# define VAR_ENCODED_SUBST_OPS      "%#:-=+?"
# define VAR_SUBST_OPS              "%#:-=+?"
# define MINUS_PLUS_EQUAL_QUESTION ("%#:-=+?" + 3)
#endif

#define SPECIAL_VAR_SYMBOL   3

struct variable;

static const char hush_version_str[] ALIGN1 = "HUSH_VERSION="BB_VER;

/* This supports saving pointers malloced in vfork child,
 * to be freed in the parent.
 */
#if !BB_MMU
typedef struct nommu_save_t {
    char **new_env;
    struct variable *old_vars;
    char **argv;
    char **argv_from_re_execing;
} nommu_save_t;
#endif

enum {
    RES_NONE  = 0,
#if ENABLE_HUSH_IF
    RES_IF    ,
    RES_THEN  ,
    RES_ELIF  ,
    RES_ELSE  ,
    RES_FI    ,
#endif
#if ENABLE_HUSH_LOOPS
    RES_FOR   ,
    RES_WHILE ,
    RES_UNTIL ,
    RES_DO    ,
    RES_DONE  ,
#endif
#if ENABLE_HUSH_LOOPS || ENABLE_HUSH_CASE
    RES_IN    ,
#endif
#if ENABLE_HUSH_CASE
    RES_CASE  ,
    /* three pseudo-keywords support contrived "case" syntax: */
    RES_CASE_IN,   /* "case ... IN", turns into RES_MATCH when IN is observed */
    RES_MATCH ,    /* "word)" */
    RES_CASE_BODY, /* "this command is inside CASE" */
    RES_ESAC  ,
#endif
    RES_XXXX  ,
    RES_SNTX
};

typedef struct o_string {
    char *data;
    int length; /* position where data is appended */
    int maxlen;
    int o_expflags;
    /* At least some part of the string was inside '' or "",
     * possibly empty one: word"", wo''rd etc. */
    smallint has_quoted_part;
    smallint has_empty_slot;
    smallint o_assignment; /* 0:maybe, 1:yes, 2:no */
} o_string;
enum {
    EXP_FLAG_SINGLEWORD     = 0x80, /* must be 0x80 */
    EXP_FLAG_GLOB           = 0x2,
    /* Protect newly added chars against globbing
     * by prepending \ to *, ?, [, \ */
    EXP_FLAG_ESC_GLOB_CHARS = 0x1,
};
enum {
    MAYBE_ASSIGNMENT      = 0,
    DEFINITELY_ASSIGNMENT = 1,
    NOT_ASSIGNMENT        = 2,
    /* Not an assignment, but next word may be: "if v=xyz cmd;" */
    WORD_IS_KEYWORD       = 3,
};
/* Used for initialization: o_string foo = NULL_O_STRING; */
#define NULL_O_STRING { NULL }

#ifndef debug_printf_parse
static const char *const assignment_flag[] = {
    "MAYBE_ASSIGNMENT",
    "DEFINITELY_ASSIGNMENT",
    "NOT_ASSIGNMENT",
    "WORD_IS_KEYWORD",
};
#endif

typedef struct in_str {
    const char *p;
    /* eof_flag=1: last char in ->p is really an EOF */
    char eof_flag; /* meaningless if ->p == NULL */
    char peek_buf[2];
#if ENABLE_HUSH_INTERACTIVE
    smallint promptmode; /* 0: PS1, 1: PS2 */
#endif
    int last_char;
    FILE *file;
    int (*get) (struct in_str *) FAST_FUNC;
    int (*peek) (struct in_str *) FAST_FUNC;
} in_str;
#define i_getch(input) ((input)->get(input))
#define i_peek(input) ((input)->peek(input))

/* The descrip member of this structure is only used to make
 * debugging output pretty */
static const struct {
    int mode;
    signed char default_fd;
    char descrip[3];
} redir_table[] = {
    { O_RDONLY,                  0, "<"  },
    { O_CREAT|O_TRUNC|O_WRONLY,  1, ">"  },
    { O_CREAT|O_APPEND|O_WRONLY, 1, ">>" },
    { O_CREAT|O_RDWR,            1, "<>" },
    { O_RDONLY,                  0, "<<" },
/* Should not be needed. Bogus default_fd helps in debugging */
/*  { O_RDONLY,                 77, "<<" }, */
};

struct redir_struct {
    struct redir_struct *next;
    char *rd_filename;          /* filename */
    int rd_fd;                  /* fd to redirect */
    /* fd to redirect to, or -3 if rd_fd is to be closed (n>&-) */
    int rd_dup;
    smallint rd_type;           /* (enum redir_type) */
    /* note: for heredocs, rd_filename contains heredoc delimiter,
     * and subsequently heredoc itself; and rd_dup is a bitmask:
     * bit 0: do we need to trim leading tabs?
     * bit 1: is heredoc quoted (<<'delim' syntax) ?
     */
};
typedef enum redir_type {
    REDIRECT_INPUT     = 0,
    REDIRECT_OVERWRITE = 1,
    REDIRECT_APPEND    = 2,
    REDIRECT_IO        = 3,
    REDIRECT_HEREDOC   = 4,
    REDIRECT_HEREDOC2  = 5, /* REDIRECT_HEREDOC after heredoc is loaded */

    REDIRFD_CLOSE      = -3,
    REDIRFD_SYNTAX_ERR = -2,
    REDIRFD_TO_FILE    = -1,
    /* otherwise, rd_fd is redirected to rd_dup */

    HEREDOC_SKIPTABS = 1,
    HEREDOC_QUOTED   = 2,
} redir_type;


struct command {
    pid_t pid;                  /* 0 if exited */
    int assignment_cnt;         /* how many argv[i] are assignments? */
    smallint cmd_type;          /* CMD_xxx */
#define CMD_NORMAL   0
#define CMD_SUBSHELL 1
#if ENABLE_HUSH_BASH_COMPAT
/* used for "[[ EXPR ]]" */
# define CMD_SINGLEWORD_NOGLOB 2
#endif
#if ENABLE_HUSH_FUNCTIONS
# define CMD_FUNCDEF 3
#endif

    smalluint cmd_exitcode;
    /* if non-NULL, this "command" is { list }, ( list ), or a compound statement */
    struct pipe *group;
#if !BB_MMU
    char *group_as_string;
#endif
#if ENABLE_HUSH_FUNCTIONS
    struct function *child_func;
/* This field is used to prevent a bug here:
 * while...do f1() {a;}; f1; f1() {b;}; f1; done
 * When we execute "f1() {a;}" cmd, we create new function and clear
 * cmd->group, cmd->group_as_string, cmd->argv[0].
 * When we execute "f1() {b;}", we notice that f1 exists,
 * and that its "parent cmd" struct is still "alive",
 * we put those fields back into cmd->xxx
 * (struct function has ->parent_cmd ptr to facilitate that).
 * When we loop back, we can execute "f1() {a;}" again and set f1 correctly.
 * Without this trick, loop would execute a;b;b;b;...
 * instead of correct sequence a;b;a;b;...
 * When command is freed, it severs the link
 * (sets ->child_func->parent_cmd to NULL).
 */
#endif
    char **argv;                /* command name and arguments */
/* argv vector may contain variable references (^Cvar^C, ^C0^C etc)
 * and on execution these are substituted with their values.
 * Substitution can make _several_ words out of one argv[n]!
 * Example: argv[0]=='.^C*^C.' here: echo .$*.
 * References of the form ^C`cmd arg^C are `cmd arg` substitutions.
 */
    struct redir_struct *redirects; /* I/O redirections */
};
/* Is there anything in this command at all? */
#define IS_NULL_CMD(cmd) \
    (!(cmd)->group && !(cmd)->argv && !(cmd)->redirects)

struct pipe {
    struct pipe *next;
    int num_cmds;               /* total number of commands in pipe */
    int alive_cmds;             /* number of commands running (not exited) */
    int stopped_cmds;           /* number of commands alive, but stopped */
#if ENABLE_HUSH_JOB
    int jobid;                  /* job number */
    pid_t pgrp;                 /* process group ID for the job */
    char *cmdtext;              /* name of job */
#endif
    struct command *cmds;       /* array of commands in pipe */
    smallint followup;          /* PIPE_BG, PIPE_SEQ, PIPE_OR, PIPE_AND */
    IF_HAS_KEYWORDS(smallint pi_inverted;) /* "! cmd | cmd" */
    IF_HAS_KEYWORDS(smallint res_word;) /* needed for if, for, while, until... */
};
typedef enum pipe_style {
    PIPE_SEQ = 1,
    PIPE_AND = 2,
    PIPE_OR  = 3,
    PIPE_BG  = 4,
} pipe_style;
/* Is there anything in this pipe at all? */
#define IS_NULL_PIPE(pi) \
    ((pi)->num_cmds == 0 IF_HAS_KEYWORDS( && (pi)->res_word == RES_NONE))

/* This holds pointers to the various results of parsing */
struct parse_context {
    /* linked list of pipes */
    struct pipe *list_head;
    /* last pipe (being constructed right now) */
    struct pipe *pipe;
    /* last command in pipe (being constructed right now) */
    struct command *command;
    /* last redirect in command->redirects list */
    struct redir_struct *pending_redirect;
#if !BB_MMU
    o_string as_string;
#endif
#if HAS_KEYWORDS
    smallint ctx_res_w;
    smallint ctx_inverted; /* "! cmd | cmd" */
#if ENABLE_HUSH_CASE
    smallint ctx_dsemicolon; /* ";;" seen */
#endif
    /* bitmask of FLAG_xxx, for figuring out valid reserved words */
    int old_flag;
    /* group we are enclosed in:
     * example: "if pipe1; pipe2; then pipe3; fi"
     * when we see "if" or "then", we malloc and copy current context,
     * and make ->stack point to it. then we parse pipeN.
     * when closing "then" / fi" / whatever is found,
     * we move list_head into ->stack->command->group,
     * copy ->stack into current context, and delete ->stack.
     * (parsing of { list } and ( list ) doesn't use this method)
     */
    struct parse_context *stack;
#endif
};

/* On program start, environ points to initial environment.
 * putenv adds new pointers into it, unsetenv removes them.
 * Neither of these (de)allocates the strings.
 * setenv allocates new strings in malloc space and does putenv,
 * and thus setenv is unusable (leaky) for shell's purposes */
#define setenv(...) setenv_is_leaky_dont_use()
struct variable {
    struct variable *next;
    char *varstr;        /* points to "name=" portion */
#if ENABLE_HUSH_LOCAL
    unsigned func_nest_level;
#endif
    int max_len;         /* if > 0, name is part of initial env; else name is malloced */
    smallint flg_export; /* putenv should be done on this var */
    smallint flg_read_only;
};

enum {
    BC_BREAK = 1,
    BC_CONTINUE = 2,
};

#if ENABLE_HUSH_FUNCTIONS
struct function {
    struct function *next;
    char *name;
    struct command *parent_cmd;
    struct pipe *body;
# if !BB_MMU
    char *body_as_string;
# endif
};
#endif


/* set -/+o OPT support. (TODO: make it optional)
 * bash supports the following opts:
 * allexport       off
 * braceexpand     on
 * emacs           on
 * errexit         off
 * errtrace        off
 * functrace       off
 * hashall         on
 * histexpand      off
 * history         on
 * ignoreeof       off
 * interactive-comments    on
 * keyword         off
 * monitor         on
 * noclobber       off
 * noexec          off
 * noglob          off
 * nolog           off
 * notify          off
 * nounset         off
 * onecmd          off
 * physical        off
 * pipefail        off
 * posix           off
 * privileged      off
 * verbose         off
 * vi              off
 * xtrace          off
 */
static const char o_opt_strings[] ALIGN1 =
    "pipefail\0"
    "noexec\0"
#if ENABLE_HUSH_MODE_X
    "xtrace\0"
#endif
    ;
enum {
    OPT_O_PIPEFAIL,
    OPT_O_NOEXEC,
#if ENABLE_HUSH_MODE_X
    OPT_O_XTRACE,
#endif
    NUM_OPT_O
};


/* "Globals" within this file */
/* Sorted roughly by size (smaller offsets == smaller code) */
struct globals {
    /* interactive_fd != 0 means we are an interactive shell.
     * If we are, then saved_tty_pgrp can also be != 0, meaning
     * that controlling tty is available. With saved_tty_pgrp == 0,
     * job control still works, but terminal signals
     * (^C, ^Z, ^Y, ^\) won't work at all, and background
     * process groups can only be created with "cmd &".
     * With saved_tty_pgrp != 0, hush will use tcsetpgrp()
     * to give tty to the foreground process group,
     * and will take it back when the group is stopped (^Z)
     * or killed (^C).
     */
#if ENABLE_HUSH_INTERACTIVE
    /* 'interactive_fd' is a fd# open to ctty, if we have one
     * _AND_ if we decided to act interactively */
    int interactive_fd;
    const char *PS1;
    const char *PS2;
# define G_interactive_fd (G.interactive_fd)
#else
# define G_interactive_fd 0
#endif
#if ENABLE_FEATURE_EDITING
    line_input_t *line_input_state;
#endif
    pid_t root_pid;
    pid_t root_ppid;
    pid_t last_bg_pid;
#if ENABLE_HUSH_RANDOM_SUPPORT
    random_t random_gen;
#endif
#if ENABLE_HUSH_JOB
    int run_list_level;
    int last_jobid;
    pid_t saved_tty_pgrp;
    struct pipe *job_list;
# define G_saved_tty_pgrp (G.saved_tty_pgrp)
#else
# define G_saved_tty_pgrp 0
#endif
    char o_opt[NUM_OPT_O];
#if ENABLE_HUSH_MODE_X
# define G_x_mode (G.o_opt[OPT_O_XTRACE])
#else
# define G_x_mode 0
#endif
    smallint flag_SIGINT;
#if ENABLE_HUSH_LOOPS
    smallint flag_break_continue;
#endif
#if ENABLE_HUSH_FUNCTIONS
    /* 0: outside of a function (or sourced file)
     * -1: inside of a function, ok to use return builtin
     * 1: return is invoked, skip all till end of func
     */
    smallint flag_return_in_progress;
#endif
    smallint exiting; /* used to prevent EXIT trap recursion */
    /* These four support $?, $#, and $1 */
    smalluint last_exitcode;
    /* are global_argv and global_argv[1..n] malloced? (note: not [0]) */
    smalluint global_args_malloced;
    /* how many non-NULL argv's we have. NB: $# + 1 */
    int global_argc;
    char **global_argv;
#if !BB_MMU
    char *argv0_for_re_execing;
#endif
#if ENABLE_HUSH_LOOPS
    unsigned depth_break_continue;
    unsigned depth_of_loop;
#endif
    const char *ifs;
    const char *cwd;
    struct variable *top_var;
    char **expanded_assignments;
#if ENABLE_HUSH_FUNCTIONS
    struct function *top_func;
# if ENABLE_HUSH_LOCAL
    struct variable **shadowed_vars_pp;
    unsigned func_nest_level;
# endif
#endif
    /* Signal and trap handling */
#if ENABLE_HUSH_FAST
    unsigned count_SIGCHLD;
    unsigned handled_SIGCHLD;
    smallint we_have_children;
#endif
    /* Which signals have non-DFL handler (even with no traps set)?
     * Set at the start to:
     * (SIGQUIT + maybe SPECIAL_INTERACTIVE_SIGS + maybe SPECIAL_JOBSTOP_SIGS)
     * SPECIAL_INTERACTIVE_SIGS are cleared after fork.
     * The rest is cleared right before execv syscalls.
     * Other than these two times, never modified.
     */
    unsigned special_sig_mask;
#if ENABLE_HUSH_JOB
    unsigned fatal_sig_mask;
# define G_fatal_sig_mask G.fatal_sig_mask
#else
# define G_fatal_sig_mask 0
#endif
    char **traps; /* char *traps[NSIG] */
    sigset_t pending_set;
#if HUSH_DEBUG
    unsigned long memleak_value;
    int debug_indent;
#endif
    struct sigaction sa;
    char user_input_buf[ENABLE_FEATURE_EDITING ? CONFIG_FEATURE_EDITING_MAX_LEN : 2];
};
#define G (*ptr_to_globals)
/* Not #defining name to G.name - this quickly gets unwieldy
 * (too many defines). Also, I actually prefer to see when a variable
 * is global, thus "G." prefix is a useful hint */
#define INIT_G() do { \
    SET_PTR_TO_GLOBALS(xzalloc(sizeof(G))); \
    /* memset(&G.sa, 0, sizeof(G.sa)); */  \
    sigfillset(&G.sa.sa_mask); \
    G.sa.sa_flags = SA_RESTART; \
} while (0)


/* Function prototypes for builtins */
static int builtin_cd(char **argv) FAST_FUNC;
static int builtin_echo(char **argv) FAST_FUNC;
static int builtin_eval(char **argv) FAST_FUNC;
static int builtin_exec(char **argv) FAST_FUNC;
static int builtin_exit(char **argv) FAST_FUNC;
static int builtin_export(char **argv) FAST_FUNC;
#if ENABLE_HUSH_JOB
static int builtin_fg_bg(char **argv) FAST_FUNC;
static int builtin_jobs(char **argv) FAST_FUNC;
#endif
#if ENABLE_HUSH_HELP
static int builtin_help(char **argv) FAST_FUNC;
#endif
#if MAX_HISTORY && ENABLE_FEATURE_EDITING
static int builtin_history(char **argv) FAST_FUNC;
#endif
#if ENABLE_HUSH_LOCAL
static int builtin_local(char **argv) FAST_FUNC;
#endif
#if HUSH_DEBUG
static int builtin_memleak(char **argv) FAST_FUNC;
#endif
#if ENABLE_PRINTF
static int builtin_printf(char **argv) FAST_FUNC;
#endif
static int builtin_pwd(char **argv) FAST_FUNC;
static int builtin_read(char **argv) FAST_FUNC;
static int builtin_set(char **argv) FAST_FUNC;
static int builtin_shift(char **argv) FAST_FUNC;
static int builtin_source(char **argv) FAST_FUNC;
static int builtin_test(char **argv) FAST_FUNC;
static int builtin_trap(char **argv) FAST_FUNC;
static int builtin_type(char **argv) FAST_FUNC;
static int builtin_true(char **argv) FAST_FUNC;
static int builtin_umask(char **argv) FAST_FUNC;
static int builtin_unset(char **argv) FAST_FUNC;
static int builtin_wait(char **argv) FAST_FUNC;
#if ENABLE_HUSH_LOOPS
static int builtin_break(char **argv) FAST_FUNC;
static int builtin_continue(char **argv) FAST_FUNC;
#endif
#if ENABLE_HUSH_FUNCTIONS
static int builtin_return(char **argv) FAST_FUNC;
#endif

/* Table of built-in functions.  They can be forked or not, depending on
 * context: within pipes, they fork.  As simple commands, they do not.
 * When used in non-forking context, they can change global variables
 * in the parent shell process.  If forked, of course they cannot.
 * For example, 'unset foo | whatever' will parse and run, but foo will
 * still be set at the end. */
struct built_in_command {
    const char *b_cmd;
    int (*b_function)(char **argv) FAST_FUNC;
#if ENABLE_HUSH_HELP
    const char *b_descr;
# define BLTIN(cmd, func, help) { cmd, func, help }
#else
# define BLTIN(cmd, func, help) { cmd, func }
#endif
};

static const struct built_in_command bltins1[] = {
    BLTIN("."        , builtin_source  , "Run commands in a file"),
    BLTIN(":"        , builtin_true    , NULL),
#if ENABLE_HUSH_JOB
    BLTIN("bg"       , builtin_fg_bg   , "Resume a job in the background"),
#endif
#if ENABLE_HUSH_LOOPS
    BLTIN("break"    , builtin_break   , "Exit from a loop"),
#endif
    BLTIN("cd"       , builtin_cd      , "Change directory"),
#if ENABLE_HUSH_LOOPS
    BLTIN("continue" , builtin_continue, "Start new loop iteration"),
#endif
    BLTIN("eval"     , builtin_eval    , "Construct and run shell command"),
    BLTIN("exec"     , builtin_exec    , "Execute command, don't return to shell"),
    BLTIN("exit"     , builtin_exit    , "Exit"),
    BLTIN("export"   , builtin_export  , "Set environment variables"),
#if ENABLE_HUSH_JOB
    BLTIN("fg"       , builtin_fg_bg   , "Bring job into the foreground"),
#endif
#if ENABLE_HUSH_HELP
    BLTIN("help"     , builtin_help    , NULL),
#endif
#if MAX_HISTORY && ENABLE_FEATURE_EDITING
    BLTIN("history"  , builtin_history , "Show command history"),
#endif
#if ENABLE_HUSH_JOB
    BLTIN("jobs"     , builtin_jobs    , "List jobs"),
#endif
#if ENABLE_HUSH_LOCAL
    BLTIN("local"    , builtin_local   , "Set local variables"),
#endif
#if HUSH_DEBUG
    BLTIN("memleak"  , builtin_memleak , NULL),
#endif
    BLTIN("read"     , builtin_read    , "Input into variable"),
#if ENABLE_HUSH_FUNCTIONS
    BLTIN("return"   , builtin_return  , "Return from a function"),
#endif
    BLTIN("set"      , builtin_set     , "Set/unset positional parameters"),
    BLTIN("shift"    , builtin_shift   , "Shift positional parameters"),
#if ENABLE_HUSH_BASH_COMPAT
    BLTIN("source"   , builtin_source  , "Run commands in a file"),
#endif
    BLTIN("trap"     , builtin_trap    , "Trap signals"),
    BLTIN("true"     , builtin_true    , NULL),
    BLTIN("type"     , builtin_type    , "Show command type"),
    BLTIN("ulimit"   , shell_builtin_ulimit  , "Control resource limits"),
    BLTIN("umask"    , builtin_umask   , "Set file creation mask"),
    BLTIN("unset"    , builtin_unset   , "Unset variables"),
    BLTIN("wait"     , builtin_wait    , "Wait for process"),
};
/* For now, echo and test are unconditionally enabled.
 * Maybe make it configurable? */
static const struct built_in_command bltins2[] = {
    BLTIN("["        , builtin_test    , NULL),
    BLTIN("echo"     , builtin_echo    , NULL),
#if ENABLE_PRINTF
    BLTIN("printf"   , builtin_printf  , NULL),
#endif
    BLTIN("pwd"      , builtin_pwd     , NULL),
    BLTIN("test"     , builtin_test    , NULL),
};


/* Debug printouts.
 */
#if HUSH_DEBUG
/* prevent disasters with G.debug_indent < 0 */
# define indent() fdprintf(2, "%*s", (G.debug_indent * 2) & 0xff, "")
# define debug_enter() (G.debug_indent++)
# define debug_leave() (G.debug_indent--)
#else
# define indent()      ((void)0)
# define debug_enter() ((void)0)
# define debug_leave() ((void)0)
#endif

#ifndef debug_printf
# define debug_printf(...) (indent(), fdprintf(2, __VA_ARGS__))
#endif

#ifndef debug_printf_parse
# define debug_printf_parse(...) (indent(), fdprintf(2, __VA_ARGS__))
#endif

#ifndef debug_printf_exec
#define debug_printf_exec(...) (indent(), fdprintf(2, __VA_ARGS__))
#endif

#ifndef debug_printf_env
# define debug_printf_env(...) (indent(), fdprintf(2, __VA_ARGS__))
#endif

#ifndef debug_printf_jobs
# define debug_printf_jobs(...) (indent(), fdprintf(2, __VA_ARGS__))
# define DEBUG_JOBS 1
#else
# define DEBUG_JOBS 0
#endif

#ifndef debug_printf_expand
# define debug_printf_expand(...) (indent(), fdprintf(2, __VA_ARGS__))
# define DEBUG_EXPAND 1
#else
# define DEBUG_EXPAND 0
#endif

#ifndef debug_printf_varexp
# define debug_printf_varexp(...) (indent(), fdprintf(2, __VA_ARGS__))
#endif

#ifndef debug_printf_glob
# define debug_printf_glob(...) (indent(), fdprintf(2, __VA_ARGS__))
# define DEBUG_GLOB 1
#else
# define DEBUG_GLOB 0
#endif

#ifndef debug_printf_list
# define debug_printf_list(...) (indent(), fdprintf(2, __VA_ARGS__))
#endif

#ifndef debug_printf_subst
# define debug_printf_subst(...) (indent(), fdprintf(2, __VA_ARGS__))
#endif

#ifndef debug_printf_clean
# define debug_printf_clean(...) (indent(), fdprintf(2, __VA_ARGS__))
# define DEBUG_CLEAN 1
#else
# define DEBUG_CLEAN 0
#endif

#if DEBUG_EXPAND
static void debug_print_strings(const char *prefix, char **vv)
{
    indent();
    fdprintf(2, "%s:\n", prefix);
    while (*vv)
        fdprintf(2, " '%s'\n", *vv++);
}
#else
# define debug_print_strings(prefix, vv) ((void)0)
#endif


/* Leak hunting. Use hush_leaktool.sh for post-processing.
 */
#if LEAK_HUNTING
static void *xxmalloc(int lineno, size_t size)
{
    void *ptr = xmalloc((size + 0xff) & ~0xff);
    fdprintf(2, "line %d: malloc %p\n", lineno, ptr);
    return ptr;
}
static void *xxrealloc(int lineno, void *ptr, size_t size)
{
    ptr = xrealloc(ptr, (size + 0xff) & ~0xff);
    fdprintf(2, "line %d: realloc %p\n", lineno, ptr);
    return ptr;
}
static char *xxstrdup(int lineno, const char *str)
{
    char *ptr = xstrdup(str);
    fdprintf(2, "line %d: strdup %p\n", lineno, ptr);
    return ptr;
}
static void xxfree(void *ptr)
{
    fdprintf(2, "free %p\n", ptr);
    free(ptr);
}
# define xmalloc(s)     xxmalloc(__LINE__, s)
# define xrealloc(p, s) xxrealloc(__LINE__, p, s)
# define xstrdup(s)     xxstrdup(__LINE__, s)
# define free(p)        xxfree(p)
#endif


/* Syntax and runtime errors. They always abort scripts.
 * In interactive use they usually discard unparsed and/or unexecuted commands
 * and return to the prompt.
 * HUSH_DEBUG >= 2 prints line number in this file where it was detected.
 */
#if HUSH_DEBUG < 2
# define die_if_script(lineno, ...)             die_if_script(__VA_ARGS__)
# define syntax_error(lineno, msg)              syntax_error(msg)
# define syntax_error_at(lineno, msg)           syntax_error_at(msg)
# define syntax_error_unterm_ch(lineno, ch)     syntax_error_unterm_ch(ch)
# define syntax_error_unterm_str(lineno, s)     syntax_error_unterm_str(s)
# define syntax_error_unexpected_ch(lineno, ch) syntax_error_unexpected_ch(ch)
#endif

static void die_if_script(unsigned lineno, const char *fmt, ...)
{
    va_list p;

#if HUSH_DEBUG >= 2
    bb_error_msg("hush.c:%u", lineno);
#endif
    va_start(p, fmt);
    bb_verror_msg(fmt, p, NULL);
    va_end(p);
    if (!G_interactive_fd)
        xfunc_die();
}

static void syntax_error(unsigned lineno UNUSED_PARAM, const char *msg)
{
    if (msg)
        bb_error_msg("syntax error: %s", msg);
    else
        bb_error_msg("syntax error");
}

static void syntax_error_at(unsigned lineno UNUSED_PARAM, const char *msg)
{
    bb_error_msg("syntax error at '%s'", msg);
}

static void syntax_error_unterm_str(unsigned lineno UNUSED_PARAM, const char *s)
{
    bb_error_msg("syntax error: unterminated %s", s);
}

static void syntax_error_unterm_ch(unsigned lineno, char ch)
{
    char msg[2] = { ch, '\0' };
    syntax_error_unterm_str(lineno, msg);
}

static void syntax_error_unexpected_ch(unsigned lineno UNUSED_PARAM, int ch)
{
    char msg[2];
    msg[0] = ch;
    msg[1] = '\0';
    bb_error_msg("syntax error: unexpected %s", ch == EOF ? "EOF" : msg);
}

#if HUSH_DEBUG < 2
# undef die_if_script
# undef syntax_error
# undef syntax_error_at
# undef syntax_error_unterm_ch
# undef syntax_error_unterm_str
# undef syntax_error_unexpected_ch
#else
# define die_if_script(...)             die_if_script(__LINE__, __VA_ARGS__)
# define syntax_error(msg)              syntax_error(__LINE__, msg)
# define syntax_error_at(msg)           syntax_error_at(__LINE__, msg)
# define syntax_error_unterm_ch(ch)     syntax_error_unterm_ch(__LINE__, ch)
# define syntax_error_unterm_str(s)     syntax_error_unterm_str(__LINE__, s)
# define syntax_error_unexpected_ch(ch) syntax_error_unexpected_ch(__LINE__, ch)
#endif


#if ENABLE_HUSH_INTERACTIVE
static void cmdedit_update_prompt(void);
#else
# define cmdedit_update_prompt() ((void)0)
#endif


/* Utility functions
 */
/* Replace each \x with x in place, return ptr past NUL. */
static char *unbackslash(char *src)
{
    char *dst = src = strchrnul(src, '\\');
    while (1) {
        if (*src == '\\')
            src++;
        if ((*dst++ = *src++) == '\0')
            break;
    }
    return dst;
}

static char **add_strings_to_strings(char **strings, char **add, int need_to_dup)
{
    int i;
    unsigned count1;
    unsigned count2;
    char **v;

    v = strings;
    count1 = 0;
    if (v) {
        while (*v) {
            count1++;
            v++;
        }
    }
    count2 = 0;
    v = add;
    while (*v) {
        count2++;
        v++;
    }
    v = xrealloc(strings, (count1 + count2 + 1) * sizeof(char*));
    v[count1 + count2] = NULL;
    i = count2;
    while (--i >= 0)
        v[count1 + i] = (need_to_dup ? xstrdup(add[i]) : add[i]);
    return v;
}
#if LEAK_HUNTING
static char **xx_add_strings_to_strings(int lineno, char **strings, char **add, int need_to_dup)
{
    char **ptr = add_strings_to_strings(strings, add, need_to_dup);
    fdprintf(2, "line %d: add_strings_to_strings %p\n", lineno, ptr);
    return ptr;
}
#define add_strings_to_strings(strings, add, need_to_dup) \
    xx_add_strings_to_strings(__LINE__, strings, add, need_to_dup)
#endif

/* Note: takes ownership of "add" ptr (it is not strdup'ed) */
static char **add_string_to_strings(char **strings, char *add)
{
    char *v[2];
    v[0] = add;
    v[1] = NULL;
    return add_strings_to_strings(strings, v, /*dup:*/ 0);
}
#if LEAK_HUNTING
static char **xx_add_string_to_strings(int lineno, char **strings, char *add)
{
    char **ptr = add_string_to_strings(strings, add);
    fdprintf(2, "line %d: add_string_to_strings %p\n", lineno, ptr);
    return ptr;
}
#define add_string_to_strings(strings, add) \
    xx_add_string_to_strings(__LINE__, strings, add)
#endif

static void free_strings(char **strings)
{
    char **v;

    if (!strings)
        return;
    v = strings;
    while (*v) {
        free(*v);
        v++;
    }
    free(strings);
}


/* Helpers for setting new $n and restoring them back
 */
typedef struct save_arg_t {
    char *sv_argv0;
    char **sv_g_argv;
    int sv_g_argc;
    smallint sv_g_malloced;
} save_arg_t;

static void save_and_replace_G_args(save_arg_t *sv, char **argv)
{
    int n;

    sv->sv_argv0 = argv[0];
    sv->sv_g_argv = G.global_argv;
    sv->sv_g_argc = G.global_argc;
    sv->sv_g_malloced = G.global_args_malloced;

    argv[0] = G.global_argv[0]; /* retain $0 */
    G.global_argv = argv;
    G.global_args_malloced = 0;

    n = 1;
    while (*++argv)
        n++;
    G.global_argc = n;
}

static void restore_G_args(save_arg_t *sv, char **argv)
{
    char **pp;

    if (G.global_args_malloced) {
        /* someone ran "set -- arg1 arg2 ...", undo */
        pp = G.global_argv;
        while (*++pp) /* note: does not free $0 */
            free(*pp);
        free(G.global_argv);
    }
    argv[0] = sv->sv_argv0;
    G.global_argv = sv->sv_g_argv;
    G.global_argc = sv->sv_g_argc;
    G.global_args_malloced = sv->sv_g_malloced;
}


/* Basic theory of signal handling in shell
 * ========================================
 * This does not describe what hush does, rather, it is current understanding
 * what it _should_ do. If it doesn't, it's a bug.
 * http://www.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#trap
 *
 * Signals are handled only after each pipe ("cmd | cmd | cmd" thing)
 * is finished or backgrounded. It is the same in interactive and
 * non-interactive shells, and is the same regardless of whether
 * a user trap handler is installed or a shell special one is in effect.
 * ^C or ^Z from keyboard seems to execute "at once" because it usually
 * backgrounds (i.e. stops) or kills all members of currently running
 * pipe.
 *
 * Wait builtin is interruptible by signals for which user trap is set
 * or by SIGINT in interactive shell.
 *
 * Trap handlers will execute even within trap handlers. (right?)
 *
 * User trap handlers are forgotten when subshell ("(cmd)") is entered,
 * except for handlers set to '' (empty string).
 *
 * If job control is off, backgrounded commands ("cmd &")
 * have SIGINT, SIGQUIT set to SIG_IGN.
 *
 * Commands which are run in command substitution ("`cmd`")
 * have SIGTTIN, SIGTTOU, SIGTSTP set to SIG_IGN.
 *
 * Ordinary commands have signals set to SIG_IGN/DFL as inherited
 * by the shell from its parent.
 *
 * Signals which differ from SIG_DFL action
 * (note: child (i.e., [v]forked) shell is not an interactive shell):
 *
 * SIGQUIT: ignore
 * SIGTERM (interactive): ignore
 * SIGHUP (interactive):
 *    send SIGCONT to stopped jobs, send SIGHUP to all jobs and exit
 * SIGTTIN, SIGTTOU, SIGTSTP (if job control is on): ignore
 *    Note that ^Z is handled not by trapping SIGTSTP, but by seeing
 *    that all pipe members are stopped. Try this in bash:
 *    while :; do :; done - ^Z does not background it
 *    (while :; do :; done) - ^Z backgrounds it
 * SIGINT (interactive): wait for last pipe, ignore the rest
 *    of the command line, show prompt. NB: ^C does not send SIGINT
 *    to interactive shell while shell is waiting for a pipe,
 *    since shell is bg'ed (is not in foreground process group).
 *    Example 1: this waits 5 sec, but does not execute ls:
 *    "echo $$; sleep 5; ls -l" + "kill -INT <pid>"
 *    Example 2: this does not wait and does not execute ls:
 *    "echo $$; sleep 5 & wait; ls -l" + "kill -INT <pid>"
 *    Example 3: this does not wait 5 sec, but executes ls:
 *    "sleep 5; ls -l" + press ^C
 *    Example 4: this does not wait and does not execute ls:
 *    "sleep 5 & wait; ls -l" + press ^C
 *
 * (What happens to signals which are IGN on shell start?)
 * (What happens with signal mask on shell start?)
 *
 * Old implementation
 * ==================
 * We use in-kernel pending signal mask to determine which signals were sent.
 * We block all signals which we don't want to take action immediately,
 * i.e. we block all signals which need to have special handling as described
 * above, and all signals which have traps set.
 * After each pipe execution, we extract any pending signals via sigtimedwait()
 * and act on them.
 *
 * unsigned special_sig_mask: a mask of such "special" signals
 * sigset_t blocked_set:  current blocked signal set
 *
 * "trap - SIGxxx":
 *    clear bit in blocked_set unless it is also in special_sig_mask
 * "trap 'cmd' SIGxxx":
 *    set bit in blocked_set (even if 'cmd' is '')
 * after [v]fork, if we plan to be a shell:
 *    unblock signals with special interactive handling
 *    (child shell is not interactive),
 *    unset all traps except '' (note: regardless of child shell's type - {}, (), etc)
 * after [v]fork, if we plan to exec:
 *    POSIX says fork clears pending signal mask in child - no need to clear it.
 *    Restore blocked signal set to one inherited by shell just prior to exec.
 *
 * Note: as a result, we do not use signal handlers much. The only uses
 * are to count SIGCHLDs
 * and to restore tty pgrp on signal-induced exit.
 *
 * Note 2 (compat):
 * Standard says "When a subshell is entered, traps that are not being ignored
 * are set to the default actions". bash interprets it so that traps which
 * are set to '' (ignore) are NOT reset to defaults. We do the same.
 *
 * Problem: the above approach makes it unwieldy to catch signals while
 * we are in read builtin, or while we read commands from stdin:
 * masked signals are not visible!
 *
 * New implementation
 * ==================
 * We record each signal we are interested in by installing signal handler
 * for them - a bit like emulating kernel pending signal mask in userspace.
 * We are interested in: signals which need to have special handling
 * as described above, and all signals which have traps set.
 * Signals are recorded in pending_set.
 * After each pipe execution, we extract any pending signals
 * and act on them.
 *
 * unsigned special_sig_mask: a mask of shell-special signals.
 * unsigned fatal_sig_mask: a mask of signals on which we restore tty pgrp.
 * char *traps[sig] if trap for sig is set (even if it's '').
 * sigset_t pending_set: set of sigs we received.
 *
 * "trap - SIGxxx":
 *    if sig is in special_sig_mask, set handler back to:
 *        record_pending_signo, or to IGN if it's a tty stop signal
 *    if sig is in fatal_sig_mask, set handler back to sigexit.
 *    else: set handler back to SIG_DFL
 * "trap 'cmd' SIGxxx":
 *    set handler to record_pending_signo.
 * "trap '' SIGxxx":
 *    set handler to SIG_IGN.
 * after [v]fork, if we plan to be a shell:
 *    set signals with special interactive handling to SIG_DFL
 *    (because child shell is not interactive),
 *    unset all traps except '' (note: regardless of child shell's type - {}, (), etc)
 * after [v]fork, if we plan to exec:
 *    POSIX says fork clears pending signal mask in child - no need to clear it.
 *
 * To make wait builtin interruptible, we handle SIGCHLD as special signal,
 * otherwise (if we leave it SIG_DFL) sigsuspend in wait builtin will not wake up on it.
 *
 * Note (compat):
 * Standard says "When a subshell is entered, traps that are not being ignored
 * are set to the default actions". bash interprets it so that traps which
 * are set to '' (ignore) are NOT reset to defaults. We do the same.
 */
enum {
    SPECIAL_INTERACTIVE_SIGS = 0
        | (1 << SIGTERM)
        | (1 << SIGINT)
        | (1 << SIGHUP)
        ,
    SPECIAL_JOBSTOP_SIGS = 0
#if ENABLE_HUSH_JOB
        | (1 << SIGTTIN)
        | (1 << SIGTTOU)
        | (1 << SIGTSTP)
#endif
        ,
};

static void record_pending_signo(int sig)
{
    sigaddset(&G.pending_set, sig);
#if ENABLE_HUSH_FAST
    if (sig == SIGCHLD) {
        G.count_SIGCHLD++;
//bb_error_msg("[%d] SIGCHLD_handler: G.count_SIGCHLD:%d G.handled_SIGCHLD:%d", getpid(), G.count_SIGCHLD, G.handled_SIGCHLD);
    }
#endif
}

static sighandler_t install_sighandler(int sig, sighandler_t handler)
{
    struct sigaction old_sa;

    /* We could use signal() to install handlers... almost:
     * except that we need to mask ALL signals while handlers run.
     * I saw signal nesting in strace, race window isn't small.
     * SA_RESTART is also needed, but in Linux, signal()
     * sets SA_RESTART too.
     */
    /* memset(&G.sa, 0, sizeof(G.sa)); - already done */
    /* sigfillset(&G.sa.sa_mask);      - already done */
    /* G.sa.sa_flags = SA_RESTART;     - already done */
    G.sa.sa_handler = handler;
    sigaction(sig, &G.sa, &old_sa);
    return old_sa.sa_handler;
}

static void hush_exit(int exitcode) NORETURN;
static void fflush_and__exit(void) NORETURN;
static void restore_ttypgrp_and__exit(void) NORETURN;

static void restore_ttypgrp_and__exit(void)
{
    /* xfunc has failed! die die die */
    /* no EXIT traps, this is an escape hatch! */
    G.exiting = 1;
    hush_exit(xfunc_error_retval);
}

/* Needed only on some libc:
 * It was observed that on exit(), fgetc'ed buffered data
 * gets "unwound" via lseek(fd, -NUM, SEEK_CUR).
 * With the net effect that even after fork(), not vfork(),
 * exit() in NOEXECed applet in "sh SCRIPT":
 *  noexec_applet_here
 *  echo END_OF_SCRIPT
 * lseeks fd in input FILE object from EOF to "e" in "echo END_OF_SCRIPT".
 * This makes "echo END_OF_SCRIPT" executed twice.
 * Similar problems can be seen with die_if_script() -> xfunc_die()
 * and in `cmd` handling.
 * If set as die_func(), this makes xfunc_die() exit via _exit(), not exit():
 */
static void fflush_and__exit(void)
{
    fflush_all();
    _exit(xfunc_error_retval);
}

#if ENABLE_HUSH_JOB

/* After [v]fork, in child: do not restore tty pgrp on xfunc death */
# define disable_restore_tty_pgrp_on_exit() (die_func = fflush_and__exit)
/* After [v]fork, in parent: restore tty pgrp on xfunc death */
# define enable_restore_tty_pgrp_on_exit()  (die_func = restore_ttypgrp_and__exit)

/* Restores tty foreground process group, and exits.
 * May be called as signal handler for fatal signal
 * (will resend signal to itself, producing correct exit state)
 * or called directly with -EXITCODE.
 * We also call it if xfunc is exiting.
 */
static void sigexit(int sig) NORETURN;
static void sigexit(int sig)
{
    /* Careful: we can end up here after [v]fork. Do not restore
     * tty pgrp then, only top-level shell process does that */
    if (G_saved_tty_pgrp && getpid() == G.root_pid) {
        /* Disable all signals: job control, SIGPIPE, etc.
         * Mostly paranoid measure, to prevent infinite SIGTTOU.
         */
        sigprocmask_allsigs(SIG_BLOCK);
        tcsetpgrp(G_interactive_fd, G_saved_tty_pgrp);
    }

    /* Not a signal, just exit */
    if (sig <= 0)
        _exit(- sig);

    kill_myself_with_sig(sig); /* does not return */
}
#else

# define disable_restore_tty_pgrp_on_exit() ((void)0)
# define enable_restore_tty_pgrp_on_exit()  ((void)0)

#endif

static sighandler_t pick_sighandler(unsigned sig)
{
    sighandler_t handler = SIG_DFL;
    if (sig < sizeof(unsigned)*8) {
        unsigned sigmask = (1 << sig);

#if ENABLE_HUSH_JOB
        /* is sig fatal? */
        if (G_fatal_sig_mask & sigmask)
            handler = sigexit;
        else
#endif
        /* sig has special handling? */
        if (G.special_sig_mask & sigmask) {
            handler = record_pending_signo;
            /* TTIN/TTOU/TSTP can't be set to record_pending_signo
             * in order to ignore them: they will be raised
             * in an endless loop when we try to do some
             * terminal ioctls! We do have to _ignore_ these.
             */
            if (SPECIAL_JOBSTOP_SIGS & sigmask)
                handler = SIG_IGN;
        }
    }
    return handler;
}

/* Restores tty foreground process group, and exits. */
static void hush_exit(int exitcode)
{
#if ENABLE_FEATURE_EDITING_SAVE_ON_EXIT
    save_history(G.line_input_state);
#endif

    fflush_all();
    if (G.exiting <= 0 && G.traps && G.traps[0] && G.traps[0][0]) {
        char *argv[3];
        /* argv[0] is unused */
        argv[1] = G.traps[0];
        argv[2] = NULL;
        G.exiting = 1; /* prevent EXIT trap recursion */
        /* Note: G.traps[0] is not cleared!
         * "trap" will still show it, if executed
         * in the handler */
        builtin_eval(argv);
    }

#if ENABLE_FEATURE_CLEAN_UP
    {
        struct variable *cur_var;
        if (G.cwd != bb_msg_unknown)
            free((char*)G.cwd);
        cur_var = G.top_var;
        while (cur_var) {
            struct variable *tmp = cur_var;
            if (!cur_var->max_len)
                free(cur_var->varstr);
            cur_var = cur_var->next;
            free(tmp);
        }
    }
#endif

    fflush_all();
#if ENABLE_HUSH_JOB
    sigexit(- (exitcode & 0xff));
#else
    _exit(exitcode);
#endif
}


//TODO: return a mask of ALL handled sigs?
static int check_and_run_traps(void)
{
    int last_sig = 0;

    while (1) {
        int sig;

        if (sigisemptyset(&G.pending_set))
            break;
        sig = 0;
        do {
            sig++;
            if (sigismember(&G.pending_set, sig)) {
                sigdelset(&G.pending_set, sig);
                goto got_sig;
            }
        } while (sig < NSIG);
        break;
 got_sig:
        if (G.traps && G.traps[sig]) {
            if (G.traps[sig][0]) {
                /* We have user-defined handler */
                smalluint save_rcode;
                char *argv[3];
                /* argv[0] is unused */
                argv[1] = G.traps[sig];
                argv[2] = NULL;
                save_rcode = G.last_exitcode;
                builtin_eval(argv);
                G.last_exitcode = save_rcode;
                last_sig = sig;
            } /* else: "" trap, ignoring signal */
            continue;
        }
        /* not a trap: special action */
        switch (sig) {
        case SIGINT:
            /* Builtin was ^C'ed, make it look prettier: */
            bb_putchar('\n');
            G.flag_SIGINT = 1;
            last_sig = sig;
            break;
#if ENABLE_HUSH_JOB
        case SIGHUP: {
            struct pipe *job;
            /* bash is observed to signal whole process groups,
             * not individual processes */
            for (job = G.job_list; job; job = job->next) {
                if (job->pgrp <= 0)
                    continue;
                debug_printf_exec("HUPing pgrp %d\n", job->pgrp);
                if (kill(- job->pgrp, SIGHUP) == 0)
                    kill(- job->pgrp, SIGCONT);
            }
            sigexit(SIGHUP);
        }
#endif
#if ENABLE_HUSH_FAST
        case SIGCHLD:
            G.count_SIGCHLD++;
//bb_error_msg("[%d] check_and_run_traps: G.count_SIGCHLD:%d G.handled_SIGCHLD:%d", getpid(), G.count_SIGCHLD, G.handled_SIGCHLD);
            /* Note:
             * We dont do 'last_sig = sig' here -> NOT returning this sig.
             * This simplifies wait builtin a bit.
             */
            break;
#endif
        default: /* ignored: */
            /* SIGTERM, SIGQUIT, SIGTTIN, SIGTTOU, SIGTSTP */
            /* Note:
             * We dont do 'last_sig = sig' here -> NOT returning this sig.
             * Example: wait is not interrupted by TERM
             * in interactive shell, because TERM is ignored.
             */
            break;
        }
    }
    return last_sig;
}


static const char *get_cwd(int force)
{
    if (force || G.cwd == NULL) {
        /* xrealloc_getcwd_or_warn(arg) calls free(arg),
         * we must not try to free(bb_msg_unknown) */
        if (G.cwd == bb_msg_unknown)
            G.cwd = NULL;
        G.cwd = xrealloc_getcwd_or_warn((char *)G.cwd);
        if (!G.cwd)
            G.cwd = bb_msg_unknown;
    }
    return G.cwd;
}


/*
 * Shell and environment variable support
 */
static struct variable **get_ptr_to_local_var(const char *name, unsigned len)
{
    struct variable **pp;
    struct variable *cur;

    pp = &G.top_var;
    while ((cur = *pp) != NULL) {
        if (strncmp(cur->varstr, name, len) == 0 && cur->varstr[len] == '=')
            return pp;
        pp = &cur->next;
    }
    return NULL;
}

static const char* FAST_FUNC get_local_var_value(const char *name)
{
    struct variable **vpp;
    unsigned len = strlen(name);

    if (G.expanded_assignments) {
        char **cpp = G.expanded_assignments;
        while (*cpp) {
            char *cp = *cpp;
            if (strncmp(cp, name, len) == 0 && cp[len] == '=')
                return cp + len + 1;
            cpp++;
        }
    }

    vpp = get_ptr_to_local_var(name, len);
    if (vpp)
        return (*vpp)->varstr + len + 1;

    if (strcmp(name, "PPID") == 0)
        return utoa(G.root_ppid);
    // bash compat: UID? EUID?
#if ENABLE_HUSH_RANDOM_SUPPORT
    if (strcmp(name, "RANDOM") == 0)
        return utoa(next_random(&G.random_gen));
#endif
    return NULL;
}

/* str holds "NAME=VAL" and is expected to be malloced.
 * We take ownership of it.
 * flg_export:
 *  0: do not change export flag
 *     (if creating new variable, flag will be 0)
 *  1: set export flag and putenv the variable
 * -1: clear export flag and unsetenv the variable
 * flg_read_only is set only when we handle -R var=val
 */
#if !BB_MMU && ENABLE_HUSH_LOCAL
/* all params are used */
#elif BB_MMU && ENABLE_HUSH_LOCAL
#define set_local_var(str, flg_export, local_lvl, flg_read_only) \
    set_local_var(str, flg_export, local_lvl)
#elif BB_MMU && !ENABLE_HUSH_LOCAL
#define set_local_var(str, flg_export, local_lvl, flg_read_only) \
    set_local_var(str, flg_export)
#elif !BB_MMU && !ENABLE_HUSH_LOCAL
#define set_local_var(str, flg_export, local_lvl, flg_read_only) \
    set_local_var(str, flg_export, flg_read_only)
#endif
static int set_local_var(char *str, int flg_export, int local_lvl, int flg_read_only)
{
    struct variable **var_pp;
    struct variable *cur;
    char *free_me = NULL;
    char *eq_sign;
    int name_len;

    eq_sign = strchr(str, '=');
    if (!eq_sign) { /* not expected to ever happen? */
        free(str);
        return -1;
    }

    name_len = eq_sign - str + 1; /* including '=' */
    var_pp = &G.top_var;
    while ((cur = *var_pp) != NULL) {
        if (strncmp(cur->varstr, str, name_len) != 0) {
            var_pp = &cur->next;
            continue;
        }

        /* We found an existing var with this name */
        if (cur->flg_read_only) {
#if !BB_MMU
            if (!flg_read_only)
#endif
                bb_error_msg("%s: readonly variable", str);
            free(str);
            return -1;
        }
        if (flg_export == -1) { // "&& cur->flg_export" ?
            debug_printf_env("%s: unsetenv '%s'\n", __func__, str);
            *eq_sign = '\0';
            unsetenv(str);
            *eq_sign = '=';
        }
#if ENABLE_HUSH_LOCAL
        if (cur->func_nest_level < local_lvl) {
            /* New variable is declared as local,
             * and existing one is global, or local
             * from enclosing function.
             * Remove and save old one: */
            *var_pp = cur->next;
            cur->next = *G.shadowed_vars_pp;
            *G.shadowed_vars_pp = cur;
            /* bash 3.2.33(1) and exported vars:
             * # export z=z
             * # f() { local z=a; env | grep ^z; }
             * # f
             * z=a
             * # env | grep ^z
             * z=z
             */
            if (cur->flg_export)
                flg_export = 1;
            break;
        }
#endif
        if (strcmp(cur->varstr + name_len, eq_sign + 1) == 0) {
 free_and_exp:
            free(str);
            goto exp;
        }
        if (cur->max_len != 0) {
            if (cur->max_len >= strlen(str)) {
                /* This one is from startup env, reuse space */
                strcpy(cur->varstr, str);
                goto free_and_exp;
            }
            /* Can't reuse */
            cur->max_len = 0;
            goto set_str_and_exp;
        }
        /* max_len == 0 signifies "malloced" var, which we can
         * (and have to) free. But we can't free(cur->varstr) here:
         * if cur->flg_export is 1, it is in the environment.
         * We should either unsetenv+free, or wait until putenv,
         * then putenv(new)+free(old).
         */
        free_me = cur->varstr;
        goto set_str_and_exp;
    }

    /* Not found - create new variable struct */
    cur = xzalloc(sizeof(*cur));
#if ENABLE_HUSH_LOCAL
    cur->func_nest_level = local_lvl;
#endif
    cur->next = *var_pp;
    *var_pp = cur;

 set_str_and_exp:
    cur->varstr = str;
#if !BB_MMU
    cur->flg_read_only = flg_read_only;
#endif
 exp:
    if (flg_export == 1)
        cur->flg_export = 1;
    if (name_len == 4 && cur->varstr[0] == 'P' && cur->varstr[1] == 'S')
        cmdedit_update_prompt();
    if (cur->flg_export) {
        if (flg_export == -1) {
            cur->flg_export = 0;
            /* unsetenv was already done */
        } else {
            int i;
            debug_printf_env("%s: putenv '%s'\n", __func__, cur->varstr);
            i = putenv(cur->varstr);
            /* only now we can free old exported malloced string */
            free(free_me);
            return i;
        }
    }
    free(free_me);
    return 0;
}

/* Used at startup and after each cd */
static void set_pwd_var(int exp)
{
    set_local_var(xasprintf("PWD=%s", get_cwd(/*force:*/ 1)),
        /*exp:*/ exp, /*lvl:*/ 0, /*ro:*/ 0);
}

static int unset_local_var_len(const char *name, int name_len)
{
    struct variable *cur;
    struct variable **var_pp;

    if (!name)
        return EXIT_SUCCESS;
    var_pp = &G.top_var;
    while ((cur = *var_pp) != NULL) {
        if (strncmp(cur->varstr, name, name_len) == 0 && cur->varstr[name_len] == '=') {
            if (cur->flg_read_only) {
                bb_error_msg("%s: readonly variable", name);
                return EXIT_FAILURE;
            }
            *var_pp = cur->next;
            debug_printf_env("%s: unsetenv '%s'\n", __func__, cur->varstr);
            bb_unsetenv(cur->varstr);
            if (name_len == 3 && cur->varstr[0] == 'P' && cur->varstr[1] == 'S')
                cmdedit_update_prompt();
            if (!cur->max_len)
                free(cur->varstr);
            free(cur);
            return EXIT_SUCCESS;
        }
        var_pp = &cur->next;
    }
    return EXIT_SUCCESS;
}

static int unset_local_var(const char *name)
{
    return unset_local_var_len(name, strlen(name));
}

static void unset_vars(char **strings)
{
    char **v;

    if (!strings)
        return;
    v = strings;
    while (*v) {
        const char *eq = strchrnul(*v, '=');
        unset_local_var_len(*v, (int)(eq - *v));
        v++;
    }
    free(strings);
}

static void FAST_FUNC set_local_var_from_halves(const char *name, const char *val)
{
    char *var = xasprintf("%s=%s", name, val);
    set_local_var(var, /*flags:*/ 0, /*lvl:*/ 0, /*ro:*/ 0);
}


/*
 * Helpers for "var1=val1 var2=val2 cmd" feature
 */
static void add_vars(struct variable *var)
{
    struct variable *next;

    while (var) {
        next = var->next;
        var->next = G.top_var;
        G.top_var = var;
        if (var->flg_export) {
            debug_printf_env("%s: restoring exported '%s'\n", __func__, var->varstr);
            putenv(var->varstr);
        } else {
            debug_printf_env("%s: restoring variable '%s'\n", __func__, var->varstr);
        }
        var = next;
    }
}

static struct variable *set_vars_and_save_old(char **strings)
{
    char **s;
    struct variable *old = NULL;

    if (!strings)
        return old;
    s = strings;
    while (*s) {
        struct variable *var_p;
        struct variable **var_pp;
        char *eq;

        eq = strchr(*s, '=');
        if (eq) {
            var_pp = get_ptr_to_local_var(*s, eq - *s);
            if (var_pp) {
                /* Remove variable from global linked list */
                var_p = *var_pp;
                debug_printf_env("%s: removing '%s'\n", __func__, var_p->varstr);
                *var_pp = var_p->next;
                /* Add it to returned list */
                var_p->next = old;
                old = var_p;
            }
            set_local_var(*s, /*exp:*/ 1, /*lvl:*/ 0, /*ro:*/ 0);
        }
        s++;
    }
    return old;
}


/*
 * Unicode helper
 */
static void reinit_unicode_for_hush(void)
{
    /* Unicode support should be activated even if LANG is set
     * _during_ shell execution, not only if it was set when
     * shell was started. Therefore, re-check LANG every time:
     */
    if (ENABLE_FEATURE_CHECK_UNICODE_IN_ENV
     || ENABLE_UNICODE_USING_LOCALE
        ) {
        const char *s = get_local_var_value("LC_ALL");
        if (!s) s = get_local_var_value("LC_CTYPE");
        if (!s) s = get_local_var_value("LANG");
        reinit_unicode(s);
    }
}


/*
 * in_str support
 */
static int FAST_FUNC static_get(struct in_str *i)
{
    int ch = *i->p;
    if (ch != '\0') {
        i->p++;
        i->last_char = ch;
        return ch;
    }
    return EOF;
}

static int FAST_FUNC static_peek(struct in_str *i)
{
    return *i->p;
}

#if ENABLE_HUSH_INTERACTIVE

static void cmdedit_update_prompt(void)
{
    if (ENABLE_FEATURE_EDITING_FANCY_PROMPT) {
        G.PS1 = get_local_var_value("PS1");
        if (G.PS1 == NULL)
            G.PS1 = "\\w \\$ ";
        G.PS2 = get_local_var_value("PS2");
    } else {
        G.PS1 = NULL;
    }
    if (G.PS2 == NULL)
        G.PS2 = "> ";
}

static const char *setup_prompt_string(int promptmode)
{
    const char *prompt_str;
    debug_printf("setup_prompt_string %d ", promptmode);
    if (!ENABLE_FEATURE_EDITING_FANCY_PROMPT) {
        /* Set up the prompt */
        if (promptmode == 0) { /* PS1 */
            free((char*)G.PS1);
            /* bash uses $PWD value, even if it is set by user.
             * It uses current dir only if PWD is unset.
             * We always use current dir. */
            G.PS1 = xasprintf("%s %c ", get_cwd(0), (geteuid() != 0) ? '$' : '#');
            prompt_str = G.PS1;
        } else
            prompt_str = G.PS2;
    } else
        prompt_str = (promptmode == 0) ? G.PS1 : G.PS2;
    debug_printf("result '%s'\n", prompt_str);
    return prompt_str;
}

static void get_user_input(struct in_str *i)
{
    int r;
    const char *prompt_str;

    prompt_str = setup_prompt_string(i->promptmode);
# if ENABLE_FEATURE_EDITING
    /* Enable command line editing only while a command line
     * is actually being read */
    do {
        reinit_unicode_for_hush();
        G.flag_SIGINT = 0;
        /* buglet: SIGINT will not make new prompt to appear _at once_,
         * only after <Enter>. (^C will work) */
        r = read_line_input(G.line_input_state, prompt_str, G.user_input_buf, CONFIG_FEATURE_EDITING_MAX_LEN-1, /*timeout*/ -1);
        /* catch *SIGINT* etc (^C is handled by read_line_input) */
        check_and_run_traps();
    } while (r == 0 || G.flag_SIGINT); /* repeat if ^C or SIGINT */
    i->eof_flag = (r < 0);
    if (i->eof_flag) { /* EOF/error detected */
        G.user_input_buf[0] = EOF; /* yes, it will be truncated, it's ok */
        G.user_input_buf[1] = '\0';
    }
# else
    do {
        G.flag_SIGINT = 0;
        if (i->last_char == '\0' || i->last_char == '\n') {
            /* Why check_and_run_traps here? Try this interactively:
             * $ trap 'echo INT' INT; (sleep 2; kill -INT $$) &
             * $ <[enter], repeatedly...>
             * Without check_and_run_traps, handler never runs.
             */
            check_and_run_traps();
            fputs(prompt_str, stdout);
        }
        fflush_all();
        G.user_input_buf[0] = r = fgetc(i->file);
        /*G.user_input_buf[1] = '\0'; - already is and never changed */
    } while (G.flag_SIGINT);
    i->eof_flag = (r == EOF);
# endif
    i->p = G.user_input_buf;
}

#endif  /* INTERACTIVE */

/* This is the magic location that prints prompts
 * and gets data back from the user */
static int FAST_FUNC file_get(struct in_str *i)
{
    int ch;

    /* If there is data waiting, eat it up */
    if (i->p && *i->p) {
#if ENABLE_HUSH_INTERACTIVE
 take_cached:
#endif
        ch = *i->p++;
        if (i->eof_flag && !*i->p)
            ch = EOF;
        /* note: ch is never NUL */
    } else {
        /* need to double check i->file because we might be doing something
         * more complicated by now, like sourcing or substituting. */
#if ENABLE_HUSH_INTERACTIVE
        if (G_interactive_fd && i->file == stdin) {
            do {
                get_user_input(i);
            } while (!*i->p); /* need non-empty line */
            i->promptmode = 1; /* PS2 */
            goto take_cached;
        }
#endif
        do ch = fgetc(i->file); while (ch == '\0');
    }
    debug_printf("file_get: got '%c' %d\n", ch, ch);
    i->last_char = ch;
    return ch;
}

/* All callers guarantee this routine will never
 * be used right after a newline, so prompting is not needed.
 */
static int FAST_FUNC file_peek(struct in_str *i)
{
    int ch;
    if (i->p && *i->p) {
        if (i->eof_flag && !i->p[1])
            return EOF;
        return *i->p;
        /* note: ch is never NUL */
    }
    do ch = fgetc(i->file); while (ch == '\0');
    i->eof_flag = (ch == EOF);
    i->peek_buf[0] = ch;
    i->peek_buf[1] = '\0';
    i->p = i->peek_buf;
    debug_printf("file_peek: got '%c' %d\n", ch, ch);
    return ch;
}

static void setup_file_in_str(struct in_str *i, FILE *f)
{
    memset(i, 0, sizeof(*i));
    i->peek = file_peek;
    i->get = file_get;
    /* i->promptmode = 0; - PS1 (memset did it) */
    i->file = f;
    /* i->p = NULL; */
}

static void setup_string_in_str(struct in_str *i, const char *s)
{
    memset(i, 0, sizeof(*i));
    i->peek = static_peek;
    i->get = static_get;
    /* i->promptmode = 0; - PS1 (memset did it) */
    i->p = s;
    /* i->eof_flag = 0; */
}


/*
 * o_string support
 */
#define B_CHUNK  (32 * sizeof(char*))

static void o_reset_to_empty_unquoted(o_string *o)
{
    o->length = 0;
    o->has_quoted_part = 0;
    if (o->data)
        o->data[0] = '\0';
}

static void o_free(o_string *o)
{
    free(o->data);
    memset(o, 0, sizeof(*o));
}

static ALWAYS_INLINE void o_free_unsafe(o_string *o)
{
    free(o->data);
}

static void o_grow_by(o_string *o, int len)
{
    if (o->length + len > o->maxlen) {
        o->maxlen += (2*len > B_CHUNK ? 2*len : B_CHUNK);
        o->data = xrealloc(o->data, 1 + o->maxlen);
    }
}

static void o_addchr(o_string *o, int ch)
{
    debug_printf("o_addchr: '%c' o->length=%d o=%p\n", ch, o->length, o);
    o_grow_by(o, 1);
    o->data[o->length] = ch;
    o->length++;
    o->data[o->length] = '\0';
}

static void o_addblock(o_string *o, const char *str, int len)
{
    o_grow_by(o, len);
    memcpy(&o->data[o->length], str, len);
    o->length += len;
    o->data[o->length] = '\0';
}

static void o_addstr(o_string *o, const char *str)
{
    o_addblock(o, str, strlen(str));
}

#if !BB_MMU
static void nommu_addchr(o_string *o, int ch)
{
    if (o)
        o_addchr(o, ch);
}
#else
# define nommu_addchr(o, str) ((void)0)
#endif

static void o_addstr_with_NUL(o_string *o, const char *str)
{
    o_addblock(o, str, strlen(str) + 1);
}

/*
 * HUSH_BRACE_EXPANSION code needs corresponding quoting on variable expansion side.
 * Currently, "v='{q,w}'; echo $v" erroneously expands braces in $v.
 * Apparently, on unquoted $v bash still does globbing
 * ("v='*.txt'; echo $v" prints all .txt files),
 * but NOT brace expansion! Thus, there should be TWO independent
 * quoting mechanisms on $v expansion side: one protects
 * $v from brace expansion, and other additionally protects "$v" against globbing.
 * We have only second one.
 */

#if ENABLE_HUSH_BRACE_EXPANSION
# define MAYBE_BRACES "{}"
#else
# define MAYBE_BRACES ""
#endif

/* My analysis of quoting semantics tells me that state information
 * is associated with a destination, not a source.
 */
static void o_addqchr(o_string *o, int ch)
{
    int sz = 1;
    char *found = strchr("*?[\\" MAYBE_BRACES, ch);
    if (found)
        sz++;
    o_grow_by(o, sz);
    if (found) {
        o->data[o->length] = '\\';
        o->length++;
    }
    o->data[o->length] = ch;
    o->length++;
    o->data[o->length] = '\0';
}

static void o_addQchr(o_string *o, int ch)
{
    int sz = 1;
    if ((o->o_expflags & EXP_FLAG_ESC_GLOB_CHARS)
     && strchr("*?[\\" MAYBE_BRACES, ch)
    ) {
        sz++;
        o->data[o->length] = '\\';
        o->length++;
    }
    o_grow_by(o, sz);
    o->data[o->length] = ch;
    o->length++;
    o->data[o->length] = '\0';
}

static void o_addqblock(o_string *o, const char *str, int len)
{
    while (len) {
        char ch;
        int sz;
        int ordinary_cnt = strcspn(str, "*?[\\" MAYBE_BRACES);
        if (ordinary_cnt > len) /* paranoia */
            ordinary_cnt = len;
        o_addblock(o, str, ordinary_cnt);
        if (ordinary_cnt == len)
            return; /* NUL is already added by o_addblock */
        str += ordinary_cnt;
        len -= ordinary_cnt + 1; /* we are processing + 1 char below */

        ch = *str++;
        sz = 1;
        if (ch) { /* it is necessarily one of "*?[\\" MAYBE_BRACES */
            sz++;
            o->data[o->length] = '\\';
            o->length++;
        }
        o_grow_by(o, sz);
        o->data[o->length] = ch;
        o->length++;
    }
    o->data[o->length] = '\0';
}

static void o_addQblock(o_string *o, const char *str, int len)
{
    if (!(o->o_expflags & EXP_FLAG_ESC_GLOB_CHARS)) {
        o_addblock(o, str, len);
        return;
    }
    o_addqblock(o, str, len);
}

static void o_addQstr(o_string *o, const char *str)
{
    o_addQblock(o, str, strlen(str));
}

/* A special kind of o_string for $VAR and `cmd` expansion.
 * It contains char* list[] at the beginning, which is grown in 16 element
 * increments. Actual string data starts at the next multiple of 16 * (char*).
 * list[i] contains an INDEX (int!) into this string data.
 * It means that if list[] needs to grow, data needs to be moved higher up
 * but list[i]'s need not be modified.
 * NB: remembering how many list[i]'s you have there is crucial.
 * o_finalize_list() operation post-processes this structure - calculates
 * and stores actual char* ptrs in list[]. Oh, it NULL terminates it as well.
 */
#if DEBUG_EXPAND || DEBUG_GLOB
static void debug_print_list(const char *prefix, o_string *o, int n)
{
    char **list = (char**)o->data;
    int string_start = ((n + 0xf) & ~0xf) * sizeof(list[0]);
    int i = 0;

    indent();
    fdprintf(2, "%s: list:%p n:%d string_start:%d length:%d maxlen:%d glob:%d quoted:%d escape:%d\n",
            prefix, list, n, string_start, o->length, o->maxlen,
            !!(o->o_expflags & EXP_FLAG_GLOB),
            o->has_quoted_part,
            !!(o->o_expflags & EXP_FLAG_ESC_GLOB_CHARS));
    while (i < n) {
        indent();
        fdprintf(2, " list[%d]=%d '%s' %p\n", i, (int)(uintptr_t)list[i],
                o->data + (int)(uintptr_t)list[i] + string_start,
                o->data + (int)(uintptr_t)list[i] + string_start);
        i++;
    }
    if (n) {
        const char *p = o->data + (int)(uintptr_t)list[n - 1] + string_start;
        indent();
        fdprintf(2, " total_sz:%ld\n", (long)((p + strlen(p) + 1) - o->data));
    }
}
#else
# define debug_print_list(prefix, o, n) ((void)0)
#endif

/* n = o_save_ptr_helper(str, n) "starts new string" by storing an index value
 * in list[n] so that it points past last stored byte so far.
 * It returns n+1. */
static int o_save_ptr_helper(o_string *o, int n)
{
    char **list = (char**)o->data;
    int string_start;
    int string_len;

    if (!o->has_empty_slot) {
        string_start = ((n + 0xf) & ~0xf) * sizeof(list[0]);
        string_len = o->length - string_start;
        if (!(n & 0xf)) { /* 0, 0x10, 0x20...? */
            debug_printf_list("list[%d]=%d string_start=%d (growing)\n", n, string_len, string_start);
            /* list[n] points to string_start, make space for 16 more pointers */
            o->maxlen += 0x10 * sizeof(list[0]);
            o->data = xrealloc(o->data, o->maxlen + 1);
            list = (char**)o->data;
            memmove(list + n + 0x10, list + n, string_len);
            o->length += 0x10 * sizeof(list[0]);
        } else {
            debug_printf_list("list[%d]=%d string_start=%d\n",
                    n, string_len, string_start);
        }
    } else {
        /* We have empty slot at list[n], reuse without growth */
        string_start = ((n+1 + 0xf) & ~0xf) * sizeof(list[0]); /* NB: n+1! */
        string_len = o->length - string_start;
        debug_printf_list("list[%d]=%d string_start=%d (empty slot)\n",
                n, string_len, string_start);
        o->has_empty_slot = 0;
    }
    o->has_quoted_part = 0;
    list[n] = (char*)(uintptr_t)string_len;
    return n + 1;
}

/* "What was our last o_save_ptr'ed position (byte offset relative o->data)?" */
static int o_get_last_ptr(o_string *o, int n)
{
    char **list = (char**)o->data;
    int string_start = ((n + 0xf) & ~0xf) * sizeof(list[0]);

    return ((int)(uintptr_t)list[n-1]) + string_start;
}

#if ENABLE_HUSH_BRACE_EXPANSION
/* There in a GNU extension, GLOB_BRACE, but it is not usable:
 * first, it processes even {a} (no commas), second,
 * I didn't manage to make it return strings when they don't match
 * existing files. Need to re-implement it.
 */

/* Helper */
static int glob_needed(const char *s)
{
    while (*s) {
        if (*s == '\\') {
            if (!s[1])
                return 0;
            s += 2;
            continue;
        }
        if (*s == '*' || *s == '[' || *s == '?' || *s == '{')
            return 1;
        s++;
    }
    return 0;
}
/* Return pointer to next closing brace or to comma */
static const char *next_brace_sub(const char *cp)
{
    unsigned depth = 0;
    cp++;
    while (*cp != '\0') {
        if (*cp == '\\') {
            if (*++cp == '\0')
                break;
            cp++;
            continue;
        }
        if ((*cp == '}' && depth-- == 0) || (*cp == ',' && depth == 0))
            break;
        if (*cp++ == '{')
            depth++;
    }

    return *cp != '\0' ? cp : NULL;
}
/* Recursive brace globber. Note: may garble pattern[]. */
static int glob_brace(char *pattern, o_string *o, int n)
{
    char *new_pattern_buf;
    const char *begin;
    const char *next;
    const char *rest;
    const char *p;
    size_t rest_len;

    debug_printf_glob("glob_brace('%s')\n", pattern);

    begin = pattern;
    while (1) {
        if (*begin == '\0')
            goto simple_glob;
        if (*begin == '{') {
            /* Find the first sub-pattern and at the same time
             * find the rest after the closing brace */
            next = next_brace_sub(begin);
            if (next == NULL) {
                /* An illegal expression */
                goto simple_glob;
            }
            if (*next == '}') {
                /* "{abc}" with no commas - illegal
                 * brace expr, disregard and skip it */
                begin = next + 1;
                continue;
            }
            break;
        }
        if (*begin == '\\' && begin[1] != '\0')
            begin++;
        begin++;
    }
    debug_printf_glob("begin:%s\n", begin);
    debug_printf_glob("next:%s\n", next);

    /* Now find the end of the whole brace expression */
    rest = next;
    while (*rest != '}') {
        rest = next_brace_sub(rest);
        if (rest == NULL) {
            /* An illegal expression */
            goto simple_glob;
        }
        debug_printf_glob("rest:%s\n", rest);
    }
    rest_len = strlen(++rest) + 1;

    /* We are sure the brace expression is well-formed */

    /* Allocate working buffer large enough for our work */
    new_pattern_buf = xmalloc(strlen(pattern));

    /* We have a brace expression.  BEGIN points to the opening {,
     * NEXT points past the terminator of the first element, and REST
     * points past the final }.  We will accumulate result names from
     * recursive runs for each brace alternative in the buffer using
     * GLOB_APPEND.  */

    p = begin + 1;
    while (1) {
        /* Construct the new glob expression */
        memcpy(
            mempcpy(
                mempcpy(new_pattern_buf,
                    /* We know the prefix for all sub-patterns */
                    pattern, begin - pattern),
                p, next - p),
            rest, rest_len);

        /* Note: glob_brace() may garble new_pattern_buf[].
         * That's why we re-copy prefix every time (1st memcpy above).
         */
        n = glob_brace(new_pattern_buf, o, n);
        if (*next == '}') {
            /* We saw the last entry */
            break;
        }
        p = next + 1;
        next = next_brace_sub(next);
    }
    free(new_pattern_buf);
    return n;

 simple_glob:
    {
        int gr;
        glob_t globdata;

        memset(&globdata, 0, sizeof(globdata));
        gr = glob(pattern, 0, NULL, &globdata);
        debug_printf_glob("glob('%s'):%d\n", pattern, gr);
        if (gr != 0) {
            if (gr == GLOB_NOMATCH) {
                globfree(&globdata);
                /* NB: garbles parameter */
                unbackslash(pattern);
                o_addstr_with_NUL(o, pattern);
                debug_printf_glob("glob pattern '%s' is literal\n", pattern);
                return o_save_ptr_helper(o, n);
            }
            if (gr == GLOB_NOSPACE)
                bb_error_msg_and_die(bb_msg_memory_exhausted);
            /* GLOB_ABORTED? Only happens with GLOB_ERR flag,
             * but we didn't specify it. Paranoia again. */
            bb_error_msg_and_die("glob error %d on '%s'", gr, pattern);
        }
        if (globdata.gl_pathv && globdata.gl_pathv[0]) {
            char **argv = globdata.gl_pathv;
            while (1) {
                o_addstr_with_NUL(o, *argv);
                n = o_save_ptr_helper(o, n);
                argv++;
                if (!*argv)
                    break;
            }
        }
        globfree(&globdata);
    }
    return n;
}
/* Performs globbing on last list[],
 * saving each result as a new list[].
 */
static int perform_glob(o_string *o, int n)
{
    char *pattern, *copy;

    debug_printf_glob("start perform_glob: n:%d o->data:%p\n", n, o->data);
    if (!o->data)
        return o_save_ptr_helper(o, n);
    pattern = o->data + o_get_last_ptr(o, n);
    debug_printf_glob("glob pattern '%s'\n", pattern);
    if (!glob_needed(pattern)) {
        /* unbackslash last string in o in place, fix length */
        o->length = unbackslash(pattern) - o->data;
        debug_printf_glob("glob pattern '%s' is literal\n", pattern);
        return o_save_ptr_helper(o, n);
    }

    copy = xstrdup(pattern);
    /* "forget" pattern in o */
    o->length = pattern - o->data;
    n = glob_brace(copy, o, n);
    free(copy);
    if (DEBUG_GLOB)
        debug_print_list("perform_glob returning", o, n);
    return n;
}

#else /* !HUSH_BRACE_EXPANSION */

/* Helper */
static int glob_needed(const char *s)
{
    while (*s) {
        if (*s == '\\') {
            if (!s[1])
                return 0;
            s += 2;
            continue;
        }
        if (*s == '*' || *s == '[' || *s == '?')
            return 1;
        s++;
    }
    return 0;
}
/* Performs globbing on last list[],
 * saving each result as a new list[].
 */
static int perform_glob(o_string *o, int n)
{
    glob_t globdata;
    int gr;
    char *pattern;

    debug_printf_glob("start perform_glob: n:%d o->data:%p\n", n, o->data);
    if (!o->data)
        return o_save_ptr_helper(o, n);
    pattern = o->data + o_get_last_ptr(o, n);
    debug_printf_glob("glob pattern '%s'\n", pattern);
    if (!glob_needed(pattern)) {
 literal:
        /* unbackslash last string in o in place, fix length */
        o->length = unbackslash(pattern) - o->data;
        debug_printf_glob("glob pattern '%s' is literal\n", pattern);
        return o_save_ptr_helper(o, n);
    }

    memset(&globdata, 0, sizeof(globdata));
    /* Can't use GLOB_NOCHECK: it does not unescape the string.
     * If we glob "*.\*" and don't find anything, we need
     * to fall back to using literal "*.*", but GLOB_NOCHECK
     * will return "*.\*"!
     */
    gr = glob(pattern, 0, NULL, &globdata);
    debug_printf_glob("glob('%s'):%d\n", pattern, gr);
    if (gr != 0) {
        if (gr == GLOB_NOMATCH) {
            globfree(&globdata);
            goto literal;
        }
        if (gr == GLOB_NOSPACE)
            bb_error_msg_and_die(bb_msg_memory_exhausted);
        /* GLOB_ABORTED? Only happens with GLOB_ERR flag,
         * but we didn't specify it. Paranoia again. */
        bb_error_msg_and_die("glob error %d on '%s'", gr, pattern);
    }
    if (globdata.gl_pathv && globdata.gl_pathv[0]) {
        char **argv = globdata.gl_pathv;
        /* "forget" pattern in o */
        o->length = pattern - o->data;
        while (1) {
            o_addstr_with_NUL(o, *argv);
            n = o_save_ptr_helper(o, n);
            argv++;
            if (!*argv)
                break;
        }
    }
    globfree(&globdata);
    if (DEBUG_GLOB)
        debug_print_list("perform_glob returning", o, n);
    return n;
}

#endif /* !HUSH_BRACE_EXPANSION */

/* If o->o_expflags & EXP_FLAG_GLOB, glob the string so far remembered.
 * Otherwise, just finish current list[] and start new */
static int o_save_ptr(o_string *o, int n)
{
    if (o->o_expflags & EXP_FLAG_GLOB) {
        /* If o->has_empty_slot, list[n] was already globbed
         * (if it was requested back then when it was filled)
         * so don't do that again! */
        if (!o->has_empty_slot)
            return perform_glob(o, n); /* o_save_ptr_helper is inside */
    }
    return o_save_ptr_helper(o, n);
}

/* "Please convert list[n] to real char* ptrs, and NULL terminate it." */
static char **o_finalize_list(o_string *o, int n)
{
    char **list;
    int string_start;

    n = o_save_ptr(o, n); /* force growth for list[n] if necessary */
    if (DEBUG_EXPAND)
        debug_print_list("finalized", o, n);
    debug_printf_expand("finalized n:%d\n", n);
    list = (char**)o->data;
    string_start = ((n + 0xf) & ~0xf) * sizeof(list[0]);
    list[--n] = NULL;
    while (n) {
        n--;
        list[n] = o->data + (int)(uintptr_t)list[n] + string_start;
    }
    return list;
}

static void free_pipe_list(struct pipe *pi);

/* Returns pi->next - next pipe in the list */
static struct pipe *free_pipe(struct pipe *pi)
{
    struct pipe *next;
    int i;

    debug_printf_clean("free_pipe (pid %d)\n", getpid());
    for (i = 0; i < pi->num_cmds; i++) {
        struct command *command;
        struct redir_struct *r, *rnext;

        command = &pi->cmds[i];
        debug_printf_clean("  command %d:\n", i);
        if (command->argv) {
            if (DEBUG_CLEAN) {
                int a;
                char **p;
                for (a = 0, p = command->argv; *p; a++, p++) {
                    debug_printf_clean("   argv[%d] = %s\n", a, *p);
                }
            }
            free_strings(command->argv);
            //command->argv = NULL;
        }
        /* not "else if": on syntax error, we may have both! */
        if (command->group) {
            debug_printf_clean("   begin group (cmd_type:%d)\n",
                    command->cmd_type);
            free_pipe_list(command->group);
            debug_printf_clean("   end group\n");
            //command->group = NULL;
        }
        /* else is crucial here.
         * If group != NULL, child_func is meaningless */
#if ENABLE_HUSH_FUNCTIONS
        else if (command->child_func) {
            debug_printf_exec("cmd %p releases child func at %p\n", command, command->child_func);
            command->child_func->parent_cmd = NULL;
        }
#endif
#if !BB_MMU
        free(command->group_as_string);
        //command->group_as_string = NULL;
#endif
        for (r = command->redirects; r; r = rnext) {
            debug_printf_clean("   redirect %d%s",
                    r->rd_fd, redir_table[r->rd_type].descrip);
            /* guard against the case >$FOO, where foo is unset or blank */
            if (r->rd_filename) {
                debug_printf_clean(" fname:'%s'\n", r->rd_filename);
                free(r->rd_filename);
                //r->rd_filename = NULL;
            }
            debug_printf_clean(" rd_dup:%d\n", r->rd_dup);
            rnext = r->next;
            free(r);
        }
        //command->redirects = NULL;
    }
    free(pi->cmds);   /* children are an array, they get freed all at once */
    //pi->cmds = NULL;
#if ENABLE_HUSH_JOB
    free(pi->cmdtext);
    //pi->cmdtext = NULL;
#endif

    next = pi->next;
    free(pi);
    return next;
}

static void free_pipe_list(struct pipe *pi)
{
    while (pi) {
#if HAS_KEYWORDS
        debug_printf_clean("pipe reserved word %d\n", pi->res_word);
#endif
        debug_printf_clean("pipe followup code %d\n", pi->followup);
        pi = free_pipe(pi);
    }
}


/*** Parsing routines ***/

#ifndef debug_print_tree
static void debug_print_tree(struct pipe *pi, int lvl)
{
    static const char *const PIPE[] = {
        [PIPE_SEQ] = "SEQ",
        [PIPE_AND] = "AND",
        [PIPE_OR ] = "OR" ,
        [PIPE_BG ] = "BG" ,
    };
    static const char *RES[] = {
        [RES_NONE ] = "NONE" ,
# if ENABLE_HUSH_IF
        [RES_IF   ] = "IF"   ,
        [RES_THEN ] = "THEN" ,
        [RES_ELIF ] = "ELIF" ,
        [RES_ELSE ] = "ELSE" ,
        [RES_FI   ] = "FI"   ,
# endif
# if ENABLE_HUSH_LOOPS
        [RES_FOR  ] = "FOR"  ,
        [RES_WHILE] = "WHILE",
        [RES_UNTIL] = "UNTIL",
        [RES_DO   ] = "DO"   ,
        [RES_DONE ] = "DONE" ,
# endif
# if ENABLE_HUSH_LOOPS || ENABLE_HUSH_CASE
        [RES_IN   ] = "IN"   ,
# endif
# if ENABLE_HUSH_CASE
        [RES_CASE ] = "CASE" ,
        [RES_CASE_IN ] = "CASE_IN" ,
        [RES_MATCH] = "MATCH",
        [RES_CASE_BODY] = "CASE_BODY",
        [RES_ESAC ] = "ESAC" ,
# endif
        [RES_XXXX ] = "XXXX" ,
        [RES_SNTX ] = "SNTX" ,
    };
    static const char *const CMDTYPE[] = {
        "{}",
        "()",
        "[noglob]",
# if ENABLE_HUSH_FUNCTIONS
        "func()",
# endif
    };

    int pin, prn;

    pin = 0;
    while (pi) {
        fdprintf(2, "%*spipe %d res_word=%s followup=%d %s\n", lvl*2, "",
                pin, RES[pi->res_word], pi->followup, PIPE[pi->followup]);
        prn = 0;
        while (prn < pi->num_cmds) {
            struct command *command = &pi->cmds[prn];
            char **argv = command->argv;

            fdprintf(2, "%*s cmd %d assignment_cnt:%d",
                    lvl*2, "", prn,
                    command->assignment_cnt);
            if (command->group) {
                fdprintf(2, " group %s: (argv=%p)%s%s\n",
                        CMDTYPE[command->cmd_type],
                        argv
# if !BB_MMU
                        , " group_as_string:", command->group_as_string
# else
                        , "", ""
# endif
                );
                debug_print_tree(command->group, lvl+1);
                prn++;
                continue;
            }
            if (argv) while (*argv) {
                fdprintf(2, " '%s'", *argv);
                argv++;
            }
            fdprintf(2, "\n");
            prn++;
        }
        pi = pi->next;
        pin++;
    }
}
#endif /* debug_print_tree */

static struct pipe *new_pipe(void)
{
    struct pipe *pi;
    pi = xzalloc(sizeof(struct pipe));
    /*pi->followup = 0; - deliberately invalid value */
    /*pi->res_word = RES_NONE; - RES_NONE is 0 anyway */
    return pi;
}

/* Command (member of a pipe) is complete, or we start a new pipe
 * if ctx->command is NULL.
 * No errors possible here.
 */
static int done_command(struct parse_context *ctx)
{
    /* The command is really already in the pipe structure, so
     * advance the pipe counter and make a new, null command. */
    struct pipe *pi = ctx->pipe;
    struct command *command = ctx->command;

    if (command) {
        if (IS_NULL_CMD(command)) {
            debug_printf_parse("done_command: skipping null cmd, num_cmds=%d\n", pi->num_cmds);
            goto clear_and_ret;
        }
        pi->num_cmds++;
        debug_printf_parse("done_command: ++num_cmds=%d\n", pi->num_cmds);
        //debug_print_tree(ctx->list_head, 20);
    } else {
        debug_printf_parse("done_command: initializing, num_cmds=%d\n", pi->num_cmds);
    }

    /* Only real trickiness here is that the uncommitted
     * command structure is not counted in pi->num_cmds. */
    pi->cmds = xrealloc(pi->cmds, sizeof(*pi->cmds) * (pi->num_cmds+1));
    ctx->command = command = &pi->cmds[pi->num_cmds];
 clear_and_ret:
    memset(command, 0, sizeof(*command));
    return pi->num_cmds; /* used only for 0/nonzero check */
}

static void done_pipe(struct parse_context *ctx, pipe_style type)
{
    int not_null;

    debug_printf_parse("done_pipe entered, followup %d\n", type);
    /* Close previous command */
    not_null = done_command(ctx);
    ctx->pipe->followup = type;
#if HAS_KEYWORDS
    ctx->pipe->pi_inverted = ctx->ctx_inverted;
    ctx->ctx_inverted = 0;
    ctx->pipe->res_word = ctx->ctx_res_w;
#endif

    /* Without this check, even just <enter> on command line generates
     * tree of three NOPs (!). Which is harmless but annoying.
     * IOW: it is safe to do it unconditionally. */
    if (not_null
#if ENABLE_HUSH_IF
     || ctx->ctx_res_w == RES_FI
#endif
#if ENABLE_HUSH_LOOPS
     || ctx->ctx_res_w == RES_DONE
     || ctx->ctx_res_w == RES_FOR
     || ctx->ctx_res_w == RES_IN
#endif
#if ENABLE_HUSH_CASE
     || ctx->ctx_res_w == RES_ESAC
#endif
    ) {
        struct pipe *new_p;
        debug_printf_parse("done_pipe: adding new pipe: "
                "not_null:%d ctx->ctx_res_w:%d\n",
                not_null, ctx->ctx_res_w);
        new_p = new_pipe();
        ctx->pipe->next = new_p;
        ctx->pipe = new_p;
        /* RES_THEN, RES_DO etc are "sticky" -
         * they remain set for pipes inside if/while.
         * This is used to control execution.
         * RES_FOR and RES_IN are NOT sticky (needed to support
         * cases where variable or value happens to match a keyword):
         */
#if ENABLE_HUSH_LOOPS
        if (ctx->ctx_res_w == RES_FOR
         || ctx->ctx_res_w == RES_IN)
            ctx->ctx_res_w = RES_NONE;
#endif
#if ENABLE_HUSH_CASE
        if (ctx->ctx_res_w == RES_MATCH)
            ctx->ctx_res_w = RES_CASE_BODY;
        if (ctx->ctx_res_w == RES_CASE)
            ctx->ctx_res_w = RES_CASE_IN;
#endif
        ctx->command = NULL; /* trick done_command below */
        /* Create the memory for command, roughly:
         * ctx->pipe->cmds = new struct command;
         * ctx->command = &ctx->pipe->cmds[0];
         */
        done_command(ctx);
        //debug_print_tree(ctx->list_head, 10);
    }
    debug_printf_parse("done_pipe return\n");
}

static void initialize_context(struct parse_context *ctx)
{
    memset(ctx, 0, sizeof(*ctx));
    ctx->pipe = ctx->list_head = new_pipe();
    /* Create the memory for command, roughly:
     * ctx->pipe->cmds = new struct command;
     * ctx->command = &ctx->pipe->cmds[0];
     */
    done_command(ctx);
}

/* If a reserved word is found and processed, parse context is modified
 * and 1 is returned.
 */
#if HAS_KEYWORDS
struct reserved_combo {
    char literal[6];
    unsigned char res;
    unsigned char assignment_flag;
    int flag;
};
enum {
    FLAG_END   = (1 << RES_NONE ),
# if ENABLE_HUSH_IF
    FLAG_IF    = (1 << RES_IF   ),
    FLAG_THEN  = (1 << RES_THEN ),
    FLAG_ELIF  = (1 << RES_ELIF ),
    FLAG_ELSE  = (1 << RES_ELSE ),
    FLAG_FI    = (1 << RES_FI   ),
# endif
# if ENABLE_HUSH_LOOPS
    FLAG_FOR   = (1 << RES_FOR  ),
    FLAG_WHILE = (1 << RES_WHILE),
    FLAG_UNTIL = (1 << RES_UNTIL),
    FLAG_DO    = (1 << RES_DO   ),
    FLAG_DONE  = (1 << RES_DONE ),
    FLAG_IN    = (1 << RES_IN   ),
# endif
# if ENABLE_HUSH_CASE
    FLAG_MATCH = (1 << RES_MATCH),
    FLAG_ESAC  = (1 << RES_ESAC ),
# endif
    FLAG_START = (1 << RES_XXXX ),
};

static const struct reserved_combo* match_reserved_word(o_string *word)
{
    /* Mostly a list of accepted follow-up reserved words.
     * FLAG_END means we are done with the sequence, and are ready
     * to turn the compound list into a command.
     * FLAG_START means the word must start a new compound list.
     */
    static const struct reserved_combo reserved_list[] = {
# if ENABLE_HUSH_IF
        { "!",     RES_NONE,  NOT_ASSIGNMENT  , 0 },
        { "if",    RES_IF,    MAYBE_ASSIGNMENT, FLAG_THEN | FLAG_START },
        { "then",  RES_THEN,  MAYBE_ASSIGNMENT, FLAG_ELIF | FLAG_ELSE | FLAG_FI },
        { "elif",  RES_ELIF,  MAYBE_ASSIGNMENT, FLAG_THEN },
        { "else",  RES_ELSE,  MAYBE_ASSIGNMENT, FLAG_FI   },
        { "fi",    RES_FI,    NOT_ASSIGNMENT  , FLAG_END  },
# endif
# if ENABLE_HUSH_LOOPS
        { "for",   RES_FOR,   NOT_ASSIGNMENT  , FLAG_IN | FLAG_DO | FLAG_START },
        { "while", RES_WHILE, MAYBE_ASSIGNMENT, FLAG_DO | FLAG_START },
        { "until", RES_UNTIL, MAYBE_ASSIGNMENT, FLAG_DO | FLAG_START },
        { "in",    RES_IN,    NOT_ASSIGNMENT  , FLAG_DO   },
        { "do",    RES_DO,    MAYBE_ASSIGNMENT, FLAG_DONE },
        { "done",  RES_DONE,  NOT_ASSIGNMENT  , FLAG_END  },
# endif
# if ENABLE_HUSH_CASE
        { "case",  RES_CASE,  NOT_ASSIGNMENT  , FLAG_MATCH | FLAG_START },
        { "esac",  RES_ESAC,  NOT_ASSIGNMENT  , FLAG_END  },
# endif
    };
    const struct reserved_combo *r;

    for (r = reserved_list; r < reserved_list + ARRAY_SIZE(reserved_list); r++) {
        if (strcmp(word->data, r->literal) == 0)
            return r;
    }
    return NULL;
}
/* Return 0: not a keyword, 1: keyword
 */
static int reserved_word(o_string *word, struct parse_context *ctx)
{
# if ENABLE_HUSH_CASE
    static const struct reserved_combo reserved_match = {
        "",        RES_MATCH, NOT_ASSIGNMENT , FLAG_MATCH | FLAG_ESAC
    };
# endif
    const struct reserved_combo *r;

    if (word->has_quoted_part)
        return 0;
    r = match_reserved_word(word);
    if (!r)
        return 0;

    debug_printf("found reserved word %s, res %d\n", r->literal, r->res);
# if ENABLE_HUSH_CASE
    if (r->res == RES_IN && ctx->ctx_res_w == RES_CASE_IN) {
        /* "case word IN ..." - IN part starts first MATCH part */
        r = &reserved_match;
    } else
# endif
    if (r->flag == 0) { /* '!' */
        if (ctx->ctx_inverted) { /* bash doesn't accept '! ! true' */
            syntax_error("! ! command");
            ctx->ctx_res_w = RES_SNTX;
        }
        ctx->ctx_inverted = 1;
        return 1;
    }
    if (r->flag & FLAG_START) {
        struct parse_context *old;

        old = xmalloc(sizeof(*old));
        debug_printf_parse("push stack %p\n", old);
        *old = *ctx;   /* physical copy */
        initialize_context(ctx);
        ctx->stack = old;
    } else if (/*ctx->ctx_res_w == RES_NONE ||*/ !(ctx->old_flag & (1 << r->res))) {
        syntax_error_at(word->data);
        ctx->ctx_res_w = RES_SNTX;
        return 1;
    } else {
        /* "{...} fi" is ok. "{...} if" is not
         * Example:
         * if { echo foo; } then { echo bar; } fi */
        if (ctx->command->group)
            done_pipe(ctx, PIPE_SEQ);
    }

    ctx->ctx_res_w = r->res;
    ctx->old_flag = r->flag;
    word->o_assignment = r->assignment_flag;
    debug_printf_parse("word->o_assignment='%s'\n", assignment_flag[word->o_assignment]);

    if (ctx->old_flag & FLAG_END) {
        struct parse_context *old;

        done_pipe(ctx, PIPE_SEQ);
        debug_printf_parse("pop stack %p\n", ctx->stack);
        old = ctx->stack;
        old->command->group = ctx->list_head;
        old->command->cmd_type = CMD_NORMAL;
# if !BB_MMU
        /* At this point, the compound command's string is in
         * ctx->as_string... except for the leading keyword!
         * Consider this example: "echo a | if true; then echo a; fi"
         * ctx->as_string will contain "true; then echo a; fi",
         * with "if " remaining in old->as_string!
         */
        {
            char *str;
            int len = old->as_string.length;
            /* Concatenate halves */
            o_addstr(&old->as_string, ctx->as_string.data);
            o_free_unsafe(&ctx->as_string);
            /* Find where leading keyword starts in first half */
            str = old->as_string.data + len;
            if (str > old->as_string.data)
                str--; /* skip whitespace after keyword */
            while (str > old->as_string.data && isalpha(str[-1]))
                str--;
            /* Ugh, we're done with this horrid hack */
            old->command->group_as_string = xstrdup(str);
            debug_printf_parse("pop, remembering as:'%s'\n",
                    old->command->group_as_string);
        }
# endif
        *ctx = *old;   /* physical copy */
        free(old);
    }
    return 1;
}
#endif /* HAS_KEYWORDS */

/* Word is complete, look at it and update parsing context.
 * Normal return is 0. Syntax errors return 1.
 * Note: on return, word is reset, but not o_free'd!
 */
static int done_word(o_string *word, struct parse_context *ctx)
{
    struct command *command = ctx->command;

    debug_printf_parse("done_word entered: '%s' %p\n", word->data, command);
    if (word->length == 0 && !word->has_quoted_part) {
        debug_printf_parse("done_word return 0: true null, ignored\n");
        return 0;
    }

    if (ctx->pending_redirect) {
        /* We do not glob in e.g. >*.tmp case. bash seems to glob here
         * only if run as "bash", not "sh" */
        /* http://www.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html
         * "2.7 Redirection
         * ...the word that follows the redirection operator
         * shall be subjected to tilde expansion, parameter expansion,
         * command substitution, arithmetic expansion, and quote
         * removal. Pathname expansion shall not be performed
         * on the word by a non-interactive shell; an interactive
         * shell may perform it, but shall do so only when
         * the expansion would result in one word."
         */
        ctx->pending_redirect->rd_filename = xstrdup(word->data);
        /* Cater for >\file case:
         * >\a creates file a; >\\a, >"\a", >"\\a" create file \a
         * Same with heredocs:
         * for <<\H delim is H; <<\\H, <<"\H", <<"\\H" - \H
         */
        if (ctx->pending_redirect->rd_type == REDIRECT_HEREDOC) {
            unbackslash(ctx->pending_redirect->rd_filename);
            /* Is it <<"HEREDOC"? */
            if (word->has_quoted_part) {
                ctx->pending_redirect->rd_dup |= HEREDOC_QUOTED;
            }
        }
        debug_printf_parse("word stored in rd_filename: '%s'\n", word->data);
        ctx->pending_redirect = NULL;
    } else {
#if HAS_KEYWORDS
# if ENABLE_HUSH_CASE
        if (ctx->ctx_dsemicolon
         && strcmp(word->data, "esac") != 0 /* not "... pattern) cmd;; esac" */
        ) {
            /* already done when ctx_dsemicolon was set to 1: */
            /* ctx->ctx_res_w = RES_MATCH; */
            ctx->ctx_dsemicolon = 0;
        } else
# endif
        if (!command->argv /* if it's the first word... */
# if ENABLE_HUSH_LOOPS
         && ctx->ctx_res_w != RES_FOR /* ...not after FOR or IN */
         && ctx->ctx_res_w != RES_IN
# endif
# if ENABLE_HUSH_CASE
         && ctx->ctx_res_w != RES_CASE
# endif
        ) {
            int reserved = reserved_word(word, ctx);
            debug_printf_parse("checking for reserved-ness: %d\n", reserved);
            if (reserved) {
                o_reset_to_empty_unquoted(word);
                debug_printf_parse("done_word return %d\n",
                        (ctx->ctx_res_w == RES_SNTX));
                return (ctx->ctx_res_w == RES_SNTX);
            }
# if ENABLE_HUSH_BASH_COMPAT
            if (strcmp(word->data, "[[") == 0) {
                command->cmd_type = CMD_SINGLEWORD_NOGLOB;
            }
            /* fall through */
# endif
        }
#endif
        if (command->group) {
            /* "{ echo foo; } echo bar" - bad */
            syntax_error_at(word->data);
            debug_printf_parse("done_word return 1: syntax error, "
                    "groups and arglists don't mix\n");
            return 1;
        }

        /* If this word wasn't an assignment, next ones definitely
         * can't be assignments. Even if they look like ones. */
        if (word->o_assignment != DEFINITELY_ASSIGNMENT
         && word->o_assignment != WORD_IS_KEYWORD
        ) {
            word->o_assignment = NOT_ASSIGNMENT;
        } else {
            if (word->o_assignment == DEFINITELY_ASSIGNMENT) {
                command->assignment_cnt++;
                debug_printf_parse("++assignment_cnt=%d\n", command->assignment_cnt);
            }
            debug_printf_parse("word->o_assignment was:'%s'\n", assignment_flag[word->o_assignment]);
            word->o_assignment = MAYBE_ASSIGNMENT;
        }
        debug_printf_parse("word->o_assignment='%s'\n", assignment_flag[word->o_assignment]);

        if (word->has_quoted_part
         /* optimization: and if it's ("" or '') or ($v... or `cmd`...): */
         && (word->data[0] == '\0' || word->data[0] == SPECIAL_VAR_SYMBOL)
         /* (otherwise it's known to be not empty and is already safe) */
        ) {
            /* exclude "$@" - it can expand to no word despite "" */
            char *p = word->data;
            while (p[0] == SPECIAL_VAR_SYMBOL
                && (p[1] & 0x7f) == '@'
                && p[2] == SPECIAL_VAR_SYMBOL
            ) {
                p += 3;
            }
        }
        command->argv = add_string_to_strings(command->argv, xstrdup(word->data));
        debug_print_strings("word appended to argv", command->argv);
    }

#if ENABLE_HUSH_LOOPS
    if (ctx->ctx_res_w == RES_FOR) {
        if (word->has_quoted_part
         || !is_well_formed_var_name(command->argv[0], '\0')
        ) {
            /* bash says just "not a valid identifier" */
            syntax_error("not a valid identifier in for");
            return 1;
        }
        /* Force FOR to have just one word (variable name) */
        /* NB: basically, this makes hush see "for v in ..."
         * syntax as if it is "for v; in ...". FOR and IN become
         * two pipe structs in parse tree. */
        done_pipe(ctx, PIPE_SEQ);
    }
#endif
#if ENABLE_HUSH_CASE
    /* Force CASE to have just one word */
    if (ctx->ctx_res_w == RES_CASE) {
        done_pipe(ctx, PIPE_SEQ);
    }
#endif

    o_reset_to_empty_unquoted(word);

    debug_printf_parse("done_word return 0\n");
    return 0;
}


/* Peek ahead in the input to find out if we have a "&n" construct,
 * as in "2>&1", that represents duplicating a file descriptor.
 * Return:
 * REDIRFD_CLOSE if >&- "close fd" construct is seen,
 * REDIRFD_SYNTAX_ERR if syntax error,
 * REDIRFD_TO_FILE if no & was seen,
 * or the number found.
 */
#if BB_MMU
#define parse_redir_right_fd(as_string, input) \
    parse_redir_right_fd(input)
#endif
static int parse_redir_right_fd(o_string *as_string, struct in_str *input)
{
    int ch, d, ok;

    ch = i_peek(input);
    if (ch != '&')
        return REDIRFD_TO_FILE;

    ch = i_getch(input);  /* get the & */
    nommu_addchr(as_string, ch);
    ch = i_peek(input);
    if (ch == '-') {
        ch = i_getch(input);
        nommu_addchr(as_string, ch);
        return REDIRFD_CLOSE;
    }
    d = 0;
    ok = 0;
    while (ch != EOF && isdigit(ch)) {
        d = d*10 + (ch-'0');
        ok = 1;
        ch = i_getch(input);
        nommu_addchr(as_string, ch);
        ch = i_peek(input);
    }
    if (ok) return d;

//TODO: this is the place to catch ">&file" bashism (redirect both fd 1 and 2)

    bb_error_msg("ambiguous redirect");
    return REDIRFD_SYNTAX_ERR;
}

/* Return code is 0 normal, 1 if a syntax error is detected
 */
static int parse_redirect(struct parse_context *ctx,
        int fd,
        redir_type style,
        struct in_str *input)
{
    struct command *command = ctx->command;
    struct redir_struct *redir;
    struct redir_struct **redirp;
    int dup_num;

    dup_num = REDIRFD_TO_FILE;
    if (style != REDIRECT_HEREDOC) {
        /* Check for a '>&1' type redirect */
        dup_num = parse_redir_right_fd(&ctx->as_string, input);
        if (dup_num == REDIRFD_SYNTAX_ERR)
            return 1;
    } else {
        int ch = i_peek(input);
        dup_num = (ch == '-'); /* HEREDOC_SKIPTABS bit is 1 */
        if (dup_num) { /* <<-... */
            ch = i_getch(input);
            nommu_addchr(&ctx->as_string, ch);
            ch = i_peek(input);
        }
    }

    if (style == REDIRECT_OVERWRITE && dup_num == REDIRFD_TO_FILE) {
        int ch = i_peek(input);
        if (ch == '|') {
            /* >|FILE redirect ("clobbering" >).
             * Since we do not support "set -o noclobber" yet,
             * >| and > are the same for now. Just eat |.
             */
            ch = i_getch(input);
            nommu_addchr(&ctx->as_string, ch);
        }
    }

    /* Create a new redir_struct and append it to the linked list */
    redirp = &command->redirects;
    while ((redir = *redirp) != NULL) {
        redirp = &(redir->next);
    }
    *redirp = redir = xzalloc(sizeof(*redir));
    /* redir->next = NULL; */
    /* redir->rd_filename = NULL; */
    redir->rd_type = style;
    redir->rd_fd = (fd == -1) ? redir_table[style].default_fd : fd;

    debug_printf_parse("redirect type %d %s\n", redir->rd_fd,
                redir_table[style].descrip);

    redir->rd_dup = dup_num;
    if (style != REDIRECT_HEREDOC && dup_num != REDIRFD_TO_FILE) {
        /* Erik had a check here that the file descriptor in question
         * is legit; I postpone that to "run time"
         * A "-" representation of "close me" shows up as a -3 here */
        debug_printf_parse("duplicating redirect '%d>&%d'\n",
                redir->rd_fd, redir->rd_dup);
    } else {
        /* Set ctx->pending_redirect, so we know what to do at the
         * end of the next parsed word. */
        ctx->pending_redirect = redir;
    }
    return 0;
}

/* If a redirect is immediately preceded by a number, that number is
 * supposed to tell which file descriptor to redirect.  This routine
 * looks for such preceding numbers.  In an ideal world this routine
 * needs to handle all the following classes of redirects...
 *     echo 2>foo     # redirects fd  2 to file "foo", nothing passed to echo
 *     echo 49>foo    # redirects fd 49 to file "foo", nothing passed to echo
 *     echo -2>foo    # redirects fd  1 to file "foo",    "-2" passed to echo
 *     echo 49x>foo   # redirects fd  1 to file "foo",   "49x" passed to echo
 *
 * http://www.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html
 * "2.7 Redirection
 * ... If n is quoted, the number shall not be recognized as part of
 * the redirection expression. For example:
 * echo \2>a
 * writes the character 2 into file a"
 * We are getting it right by setting ->has_quoted_part on any \<char>
 *
 * A -1 return means no valid number was found,
 * the caller should use the appropriate default for this redirection.
 */
static int redirect_opt_num(o_string *o)
{
    int num;

    if (o->data == NULL)
        return -1;
    num = bb_strtou(o->data, NULL, 10);
    if (errno || num < 0)
        return -1;
    o_reset_to_empty_unquoted(o);
    return num;
}

#if BB_MMU
#define fetch_till_str(as_string, input, word, skip_tabs) \
    fetch_till_str(input, word, skip_tabs)
#endif
static char *fetch_till_str(o_string *as_string,
        struct in_str *input,
        const char *word,
        int heredoc_flags)
{
    o_string heredoc = NULL_O_STRING;
    unsigned past_EOL;
    int prev = 0; /* not \ */
    int ch;

    goto jump_in;

    while (1) {
        ch = i_getch(input);
        if (ch != EOF)
            nommu_addchr(as_string, ch);
        if ((ch == '\n' || ch == EOF)
         && ((heredoc_flags & HEREDOC_QUOTED) || prev != '\\')
        ) {
            if (strcmp(heredoc.data + past_EOL, word) == 0) {
                heredoc.data[past_EOL] = '\0';
                debug_printf_parse("parsed heredoc '%s'\n", heredoc.data);
                return heredoc.data;
            }
            while (ch == '\n') {
                o_addchr(&heredoc, ch);
                prev = ch;
 jump_in:
                past_EOL = heredoc.length;
                do {
                    ch = i_getch(input);
                    if (ch != EOF)
                        nommu_addchr(as_string, ch);
                } while ((heredoc_flags & HEREDOC_SKIPTABS) && ch == '\t');
            }
        }
        if (ch == EOF) {
            o_free_unsafe(&heredoc);
            return NULL;
        }
        o_addchr(&heredoc, ch);
        nommu_addchr(as_string, ch);
        if (prev == '\\' && ch == '\\')
            /* Correctly handle foo\\<eol> (not a line cont.) */
            prev = 0; /* not \ */
        else
            prev = ch;
    }
}

/* Look at entire parse tree for not-yet-loaded REDIRECT_HEREDOCs
 * and load them all. There should be exactly heredoc_cnt of them.
 */
static int fetch_heredocs(int heredoc_cnt, struct parse_context *ctx, struct in_str *input)
{
    struct pipe *pi = ctx->list_head;

    while (pi && heredoc_cnt) {
        int i;
        struct command *cmd = pi->cmds;

        debug_printf_parse("fetch_heredocs: num_cmds:%d cmd argv0:'%s'\n",
                pi->num_cmds,
                cmd->argv ? cmd->argv[0] : "NONE");
        for (i = 0; i < pi->num_cmds; i++) {
            struct redir_struct *redir = cmd->redirects;

            debug_printf_parse("fetch_heredocs: %d cmd argv0:'%s'\n",
                    i, cmd->argv ? cmd->argv[0] : "NONE");
            while (redir) {
                if (redir->rd_type == REDIRECT_HEREDOC) {
                    char *p;

                    redir->rd_type = REDIRECT_HEREDOC2;
                    /* redir->rd_dup is (ab)used to indicate <<- */
                    p = fetch_till_str(&ctx->as_string, input,
                            redir->rd_filename, redir->rd_dup);
                    if (!p) {
                        syntax_error("unexpected EOF in here document");
                        return 1;
                    }
                    free(redir->rd_filename);
                    redir->rd_filename = p;
                    heredoc_cnt--;
                }
                redir = redir->next;
            }
            cmd++;
        }
        pi = pi->next;
    }
#if 0
    /* Should be 0. If it isn't, it's a parse error */
    if (heredoc_cnt)
        bb_error_msg_and_die("heredoc BUG 2");
#endif
    return 0;
}


static int run_list(struct pipe *pi);
#if BB_MMU
#define parse_stream(pstring, input, end_trigger) \
    parse_stream(input, end_trigger)
#endif
static struct pipe *parse_stream(char **pstring,
        struct in_str *input,
        int end_trigger);


#if !ENABLE_HUSH_FUNCTIONS
#define parse_group(dest, ctx, input, ch) \
    parse_group(ctx, input, ch)
#endif
static int parse_group(o_string *dest, struct parse_context *ctx,
    struct in_str *input, int ch)
{
    /* dest contains characters seen prior to ( or {.
     * Typically it's empty, but for function defs,
     * it contains function name (without '()'). */
    struct pipe *pipe_list;
    int endch;
    struct command *command = ctx->command;

    debug_printf_parse("parse_group entered\n");
#if ENABLE_HUSH_FUNCTIONS
    if (ch == '(' && !dest->has_quoted_part) {
        if (dest->length)
            if (done_word(dest, ctx))
                return 1;
        if (!command->argv)
            goto skip; /* (... */
        if (command->argv[1]) { /* word word ... (... */
            syntax_error_unexpected_ch('(');
            return 1;
        }
        /* it is "word(..." or "word (..." */
        do
            ch = i_getch(input);
        while (ch == ' ' || ch == '\t');
        if (ch != ')') {
            syntax_error_unexpected_ch(ch);
            return 1;
        }
        nommu_addchr(&ctx->as_string, ch);
        do
            ch = i_getch(input);
        while (ch == ' ' || ch == '\t' || ch == '\n');
        if (ch != '{') {
            syntax_error_unexpected_ch(ch);
            return 1;
        }
        nommu_addchr(&ctx->as_string, ch);
        command->cmd_type = CMD_FUNCDEF;
        goto skip;
    }
#endif

#if 0 /* Prevented by caller */
    if (command->argv /* word [word]{... */
     || dest->length /* word{... */
     || dest->has_quoted_part /* ""{... */
    ) {
        syntax_error(NULL);
        debug_printf_parse("parse_group return 1: "
            "syntax error, groups and arglists don't mix\n");
        return 1;
    }
#endif

#if ENABLE_HUSH_FUNCTIONS
 skip:
#endif
    endch = '}';
    if (ch == '(') {
        endch = ')';
        command->cmd_type = CMD_SUBSHELL;
    } else {
        /* bash does not allow "{echo...", requires whitespace */
        ch = i_getch(input);
        if (ch != ' ' && ch != '\t' && ch != '\n') {
            syntax_error_unexpected_ch(ch);
            return 1;
        }
        nommu_addchr(&ctx->as_string, ch);
    }

    {
#if BB_MMU
# define as_string NULL
#else
        char *as_string = NULL;
#endif
        pipe_list = parse_stream(&as_string, input, endch);
#if !BB_MMU
        if (as_string)
            o_addstr(&ctx->as_string, as_string);
#endif
        /* empty ()/{} or parse error? */
        if (!pipe_list || pipe_list == ERR_PTR) {
            /* parse_stream already emitted error msg */
            if (!BB_MMU)
                free(as_string);
            debug_printf_parse("parse_group return 1: "
                "parse_stream returned %p\n", pipe_list);
            return 1;
        }
        command->group = pipe_list;
#if !BB_MMU
        as_string[strlen(as_string) - 1] = '\0'; /* plink ')' or '}' */
        command->group_as_string = as_string;
        debug_printf_parse("end of group, remembering as:'%s'\n",
                command->group_as_string);
#endif
#undef as_string
    }
    debug_printf_parse("parse_group return 0\n");
    return 0;
    /* command remains "open", available for possible redirects */
}

#if ENABLE_HUSH_TICK || ENABLE_SH_MATH_SUPPORT || ENABLE_HUSH_DOLLAR_OPS
/* Subroutines for copying $(...) and `...` things */
static int add_till_backquote(o_string *dest, struct in_str *input, int in_dquote);
/* '...' */
static int add_till_single_quote(o_string *dest, struct in_str *input)
{
    while (1) {
        int ch = i_getch(input);
        if (ch == EOF) {
            syntax_error_unterm_ch('\'');
            return 0;
        }
        if (ch == '\'')
            return 1;
        o_addchr(dest, ch);
    }
}
/* "...\"...`..`...." - do we need to handle "...$(..)..." too? */
static int add_till_double_quote(o_string *dest, struct in_str *input)
{
    while (1) {
        int ch = i_getch(input);
        if (ch == EOF) {
            syntax_error_unterm_ch('"');
            return 0;
        }
        if (ch == '"')
            return 1;
        if (ch == '\\') {  /* \x. Copy both chars. */
            o_addchr(dest, ch);
            ch = i_getch(input);
        }
        o_addchr(dest, ch);
        if (ch == '`') {
            if (!add_till_backquote(dest, input, /*in_dquote:*/ 1))
                return 0;
            o_addchr(dest, ch);
            continue;
        }
        //if (ch == '$') ...
    }
}
/* Process `cmd` - copy contents until "`" is seen. Complicated by
 * \` quoting.
 * "Within the backquoted style of command substitution, backslash
 * shall retain its literal meaning, except when followed by: '$', '`', or '\'.
 * The search for the matching backquote shall be satisfied by the first
 * backquote found without a preceding backslash; during this search,
 * if a non-escaped backquote is encountered within a shell comment,
 * a here-document, an embedded command substitution of the $(command)
 * form, or a quoted string, undefined results occur. A single-quoted
 * or double-quoted string that begins, but does not end, within the
 * "`...`" sequence produces undefined results."
 * Example                               Output
 * echo `echo '\'TEST\`echo ZZ\`BEST`    \TESTZZBEST
 */
static int add_till_backquote(o_string *dest, struct in_str *input, int in_dquote)
{
    while (1) {
        int ch = i_getch(input);
        if (ch == '`')
            return 1;
        if (ch == '\\') {
            /* \x. Copy both unless it is \`, \$, \\ and maybe \" */
            ch = i_getch(input);
            if (ch != '`'
             && ch != '$'
             && ch != '\\'
             && (!in_dquote || ch != '"')
            ) {
                o_addchr(dest, '\\');
            }
        }
        if (ch == EOF) {
            syntax_error_unterm_ch('`');
            return 0;
        }
        o_addchr(dest, ch);
    }
}
/* Process $(cmd) - copy contents until ")" is seen. Complicated by
 * quoting and nested ()s.
 * "With the $(command) style of command substitution, all characters
 * following the open parenthesis to the matching closing parenthesis
 * constitute the command. Any valid shell script can be used for command,
 * except a script consisting solely of redirections which produces
 * unspecified results."
 * Example                              Output
 * echo $(echo '(TEST)' BEST)           (TEST) BEST
 * echo $(echo 'TEST)' BEST)            TEST) BEST
 * echo $(echo \(\(TEST\) BEST)         ((TEST) BEST
 *
 * Also adapted to eat ${var%...} and $((...)) constructs, since ... part
 * can contain arbitrary constructs, just like $(cmd).
 * In bash compat mode, it needs to also be able to stop on ':' or '/'
 * for ${var:N[:M]} and ${var/P[/R]} parsing.
 */
#define DOUBLE_CLOSE_CHAR_FLAG 0x80
static int add_till_closing_bracket(o_string *dest, struct in_str *input, unsigned end_ch)
{
    int ch;
    char dbl = end_ch & DOUBLE_CLOSE_CHAR_FLAG;
# if ENABLE_HUSH_BASH_COMPAT
    char end_char2 = end_ch >> 8;
# endif
    end_ch &= (DOUBLE_CLOSE_CHAR_FLAG - 1);

    while (1) {
        ch = i_getch(input);
        if (ch == EOF) {
            syntax_error_unterm_ch(end_ch);
            return 0;
        }
        if (ch == end_ch  IF_HUSH_BASH_COMPAT( || ch == end_char2)) {
            if (!dbl)
                break;
            /* we look for closing )) of $((EXPR)) */
            if (i_peek(input) == end_ch) {
                i_getch(input); /* eat second ')' */
                break;
            }
        }
        o_addchr(dest, ch);
        if (ch == '(' || ch == '{') {
            ch = (ch == '(' ? ')' : '}');
            if (!add_till_closing_bracket(dest, input, ch))
                return 0;
            o_addchr(dest, ch);
            continue;
        }
        if (ch == '\'') {
            if (!add_till_single_quote(dest, input))
                return 0;
            o_addchr(dest, ch);
            continue;
        }
        if (ch == '"') {
            if (!add_till_double_quote(dest, input))
                return 0;
            o_addchr(dest, ch);
            continue;
        }
        if (ch == '`') {
            if (!add_till_backquote(dest, input, /*in_dquote:*/ 0))
                return 0;
            o_addchr(dest, ch);
            continue;
        }
        if (ch == '\\') {
            /* \x. Copy verbatim. Important for  \(, \) */
            ch = i_getch(input);
            if (ch == EOF) {
                syntax_error_unterm_ch(')');
                return 0;
            }
            o_addchr(dest, ch);
            continue;
        }
    }
    return ch;
}
#endif /* ENABLE_HUSH_TICK || ENABLE_SH_MATH_SUPPORT || ENABLE_HUSH_DOLLAR_OPS */

/* Return code: 0 for OK, 1 for syntax error */
#if BB_MMU
#define parse_dollar(as_string, dest, input, quote_mask) \
    parse_dollar(dest, input, quote_mask)
#define as_string NULL
#endif
static int parse_dollar(o_string *as_string,
        o_string *dest,
        struct in_str *input, unsigned char quote_mask)
{
    int ch = i_peek(input);  /* first character after the $ */

    debug_printf_parse("parse_dollar entered: ch='%c'\n", ch);
    if (isalpha(ch)) {
        ch = i_getch(input);
        nommu_addchr(as_string, ch);
 make_var:
        o_addchr(dest, SPECIAL_VAR_SYMBOL);
        while (1) {
            debug_printf_parse(": '%c'\n", ch);
            o_addchr(dest, ch | quote_mask);
            quote_mask = 0;
            ch = i_peek(input);
            if (!isalnum(ch) && ch != '_')
                break;
            ch = i_getch(input);
            nommu_addchr(as_string, ch);
        }
        o_addchr(dest, SPECIAL_VAR_SYMBOL);
    } else if (isdigit(ch)) {
 make_one_char_var:
        ch = i_getch(input);
        nommu_addchr(as_string, ch);
        o_addchr(dest, SPECIAL_VAR_SYMBOL);
        debug_printf_parse(": '%c'\n", ch);
        o_addchr(dest, ch | quote_mask);
        o_addchr(dest, SPECIAL_VAR_SYMBOL);
    } else switch (ch) {
    case '$': /* pid */
    case '!': /* last bg pid */
    case '?': /* last exit code */
    case '#': /* number of args */
    case '*': /* args */
    case '@': /* args */
        goto make_one_char_var;
    case '{': {
        o_addchr(dest, SPECIAL_VAR_SYMBOL);

        ch = i_getch(input); /* eat '{' */
        nommu_addchr(as_string, ch);

        ch = i_getch(input); /* first char after '{' */
        /* It should be ${?}, or ${#var},
         * or even ${?+subst} - operator acting on a special variable,
         * or the beginning of variable name.
         */
        if (ch == EOF
         || (!strchr(_SPECIAL_VARS_STR, ch) && !isalnum(ch)) /* not one of those */
        ) {
 bad_dollar_syntax:
            syntax_error_unterm_str("${name}");
            debug_printf_parse("parse_dollar return 0: unterminated ${name}\n");
            return 0;
        }
        nommu_addchr(as_string, ch);
        ch |= quote_mask;

        /* It's possible to just call add_till_closing_bracket() at this point.
         * However, this regresses some of our testsuite cases
         * which check invalid constructs like ${%}.
         * Oh well... let's check that the var name part is fine... */

        while (1) {
            unsigned pos;

            o_addchr(dest, ch);
            debug_printf_parse(": '%c'\n", ch);

            ch = i_getch(input);
            nommu_addchr(as_string, ch);
            if (ch == '}')
                break;

            if (!isalnum(ch) && ch != '_') {
                unsigned end_ch;
                unsigned char last_ch;
                /* handle parameter expansions
                 * http://www.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html#tag_02_06_02
                 */
                if (!strchr(VAR_SUBST_OPS, ch)) /* ${var<bad_char>... */
                    goto bad_dollar_syntax;

                /* Eat everything until closing '}' (or ':') */
                end_ch = '}';
                if (ENABLE_HUSH_BASH_COMPAT
                 && ch == ':'
                 && !strchr(MINUS_PLUS_EQUAL_QUESTION, i_peek(input))
                ) {
                    /* It's ${var:N[:M]} thing */
                    end_ch = '}' * 0x100 + ':';
                }
                if (ENABLE_HUSH_BASH_COMPAT
                 && ch == '/'
                ) {
                    /* It's ${var/[/]pattern[/repl]} thing */
                    if (i_peek(input) == '/') { /* ${var//pattern[/repl]}? */
                        i_getch(input);
                        nommu_addchr(as_string, '/');
                        ch = '\\';
                    }
                    end_ch = '}' * 0x100 + '/';
                }
                o_addchr(dest, ch);
 again:
                if (!BB_MMU)
                    pos = dest->length;
#if ENABLE_HUSH_DOLLAR_OPS
                last_ch = add_till_closing_bracket(dest, input, end_ch);
                if (last_ch == 0) /* error? */
                    return 0;
#else
#error Simple code to only allow ${var} is not implemented
#endif
                if (as_string) {
                    o_addstr(as_string, dest->data + pos);
                    o_addchr(as_string, last_ch);
                }

                if (ENABLE_HUSH_BASH_COMPAT && (end_ch & 0xff00)) {
                    /* close the first block: */
                    o_addchr(dest, SPECIAL_VAR_SYMBOL);
                    /* while parsing N from ${var:N[:M]}
                     * or pattern from ${var/[/]pattern[/repl]} */
                    if ((end_ch & 0xff) == last_ch) {
                        /* got ':' or '/'- parse the rest */
                        end_ch = '}';
                        goto again;
                    }
                    /* got '}' */
                    if (end_ch == '}' * 0x100 + ':') {
                        /* it's ${var:N} - emulate :999999999 */
                        o_addstr(dest, "999999999");
                    } /* else: it's ${var/[/]pattern} */
                }
                break;
            }
        }
        o_addchr(dest, SPECIAL_VAR_SYMBOL);
        break;
    }
#if ENABLE_SH_MATH_SUPPORT || ENABLE_HUSH_TICK
    case '(': {
        unsigned pos;

        ch = i_getch(input);
        nommu_addchr(as_string, ch);
# if ENABLE_SH_MATH_SUPPORT
        if (i_peek(input) == '(') {
            ch = i_getch(input);
            nommu_addchr(as_string, ch);
            o_addchr(dest, SPECIAL_VAR_SYMBOL);
            o_addchr(dest, /*quote_mask |*/ '+');
            if (!BB_MMU)
                pos = dest->length;
            if (!add_till_closing_bracket(dest, input, ')' | DOUBLE_CLOSE_CHAR_FLAG))
                return 0; /* error */
            if (as_string) {
                o_addstr(as_string, dest->data + pos);
                o_addchr(as_string, ')');
                o_addchr(as_string, ')');
            }
            o_addchr(dest, SPECIAL_VAR_SYMBOL);
            break;
        }
# endif
# if ENABLE_HUSH_TICK
        o_addchr(dest, SPECIAL_VAR_SYMBOL);
        o_addchr(dest, quote_mask | '`');
        if (!BB_MMU)
            pos = dest->length;
        if (!add_till_closing_bracket(dest, input, ')'))
            return 0; /* error */
        if (as_string) {
            o_addstr(as_string, dest->data + pos);
            o_addchr(as_string, ')');
        }
        o_addchr(dest, SPECIAL_VAR_SYMBOL);
# endif
        break;
    }
#endif
    case '_':
        ch = i_getch(input);
        nommu_addchr(as_string, ch);
        ch = i_peek(input);
        if (isalnum(ch)) { /* it's $_name or $_123 */
            ch = '_';
            goto make_var;
        }
        /* else: it's $_ */
    /* TODO: $_ and $-: */
    /* $_ Shell or shell script name; or last argument of last command
     * (if last command wasn't a pipe; if it was, bash sets $_ to "");
     * but in command's env, set to full pathname used to invoke it */
    /* $- Option flags set by set builtin or shell options (-i etc) */
    default:
        o_addQchr(dest, '$');
    }
    debug_printf_parse("parse_dollar return 1 (ok)\n");
    return 1;
#undef as_string
}

#if BB_MMU
# if ENABLE_HUSH_BASH_COMPAT
#define encode_string(as_string, dest, input, dquote_end, process_bkslash) \
    encode_string(dest, input, dquote_end, process_bkslash)
# else
/* only ${var/pattern/repl} (its pattern part) needs additional mode */
#define encode_string(as_string, dest, input, dquote_end, process_bkslash) \
    encode_string(dest, input, dquote_end)
# endif
#define as_string NULL

#else /* !MMU */

# if ENABLE_HUSH_BASH_COMPAT
/* all parameters are needed, no macro tricks */
# else
#define encode_string(as_string, dest, input, dquote_end, process_bkslash) \
    encode_string(as_string, dest, input, dquote_end)
# endif
#endif
static int encode_string(o_string *as_string,
        o_string *dest,
        struct in_str *input,
        int dquote_end,
        int process_bkslash)
{
#if !ENABLE_HUSH_BASH_COMPAT
    const int process_bkslash = 1;
#endif
    int ch;
    int next;

 again:
    ch = i_getch(input);
    if (ch != EOF)
        nommu_addchr(as_string, ch);
    if (ch == dquote_end) { /* may be only '"' or EOF */
        debug_printf_parse("encode_string return 1 (ok)\n");
        return 1;
    }
    /* note: can't move it above ch == dquote_end check! */
    if (ch == EOF) {
        syntax_error_unterm_ch('"');
        return 0; /* error */
    }
    next = '\0';
    if (ch != '\n') {
        next = i_peek(input);
    }
    debug_printf_parse("\" ch=%c (%d) escape=%d\n",
            ch, ch, !!(dest->o_expflags & EXP_FLAG_ESC_GLOB_CHARS));
    if (process_bkslash && ch == '\\') {
        if (next == EOF) {
            syntax_error("\\<eof>");
            xfunc_die();
        }
        /* bash:
         * "The backslash retains its special meaning [in "..."]
         * only when followed by one of the following characters:
         * $, `, ", \, or <newline>.  A double quote may be quoted
         * within double quotes by preceding it with a backslash."
         * NB: in (unquoted) heredoc, above does not apply to ",
         * therefore we check for it by "next == dquote_end" cond.
         */
        if (next == dquote_end || strchr("$`\\\n", next)) {
            ch = i_getch(input); /* eat next */
            if (ch == '\n')
                goto again; /* skip \<newline> */
        } /* else: ch remains == '\\', and we double it below: */
        o_addqchr(dest, ch); /* \c if c is a glob char, else just c */
        nommu_addchr(as_string, ch);
        goto again;
    }
    if (ch == '$') {
        if (!parse_dollar(as_string, dest, input, /*quote_mask:*/ 0x80)) {
            debug_printf_parse("encode_string return 0: "
                    "parse_dollar returned 0 (error)\n");
            return 0;
        }
        goto again;
    }
#if ENABLE_HUSH_TICK
    if (ch == '`') {
        //unsigned pos = dest->length;
        o_addchr(dest, SPECIAL_VAR_SYMBOL);
        o_addchr(dest, 0x80 | '`');
        if (!add_till_backquote(dest, input, /*in_dquote:*/ dquote_end == '"'))
            return 0; /* error */
        o_addchr(dest, SPECIAL_VAR_SYMBOL);
        //debug_printf_subst("SUBST RES3 '%s'\n", dest->data + pos);
        goto again;
    }
#endif
    o_addQchr(dest, ch);
    goto again;
#undef as_string
}

/*
 * Scan input until EOF or end_trigger char.
 * Return a list of pipes to execute, or NULL on EOF
 * or if end_trigger character is met.
 * On syntax error, exit if shell is not interactive,
 * reset parsing machinery and start parsing anew,
 * or return ERR_PTR.
 */
static struct pipe *parse_stream(char **pstring,
        struct in_str *input,
        int end_trigger)
{
    struct parse_context ctx;
    o_string dest = NULL_O_STRING;
    int heredoc_cnt;

    /* Single-quote triggers a bypass of the main loop until its mate is
     * found.  When recursing, quote state is passed in via dest->o_expflags.
     */
    debug_printf_parse("parse_stream entered, end_trigger='%c'\n",
            end_trigger ? end_trigger : 'X');
    debug_enter();

    /* If very first arg is "" or '', dest.data may end up NULL.
     * Preventing this: */
    o_addchr(&dest, '\0');
    dest.length = 0;

    /* We used to separate words on $IFS here. This was wrong.
     * $IFS is used only for word splitting when $var is expanded,
     * here we should use blank chars as separators, not $IFS
     */

    if (MAYBE_ASSIGNMENT != 0)
        dest.o_assignment = MAYBE_ASSIGNMENT;
    initialize_context(&ctx);
    heredoc_cnt = 0;
    while (1) {
        const char *is_blank;
        const char *is_special;
        int ch;
        int next;
        int redir_fd;
        redir_type redir_style;

        ch = i_getch(input);
        debug_printf_parse(": ch=%c (%d) escape=%d\n",
                ch, ch, !!(dest.o_expflags & EXP_FLAG_ESC_GLOB_CHARS));
        if (ch == EOF) {
            struct pipe *pi;

            if (heredoc_cnt) {
                syntax_error_unterm_str("here document");
                goto parse_error;
            }
            /* end_trigger == '}' case errors out earlier,
             * checking only ')' */
            if (end_trigger == ')') {
                syntax_error_unterm_ch('(');
                goto parse_error;
            }

            if (done_word(&dest, &ctx)) {
                goto parse_error;
            }
            o_free(&dest);
            done_pipe(&ctx, PIPE_SEQ);
            pi = ctx.list_head;
            /* If we got nothing... */
            /* (this makes bare "&" cmd a no-op.
             * bash says: "syntax error near unexpected token '&'") */
            if (pi->num_cmds == 0
            IF_HAS_KEYWORDS(&& pi->res_word == RES_NONE)
            ) {
                free_pipe_list(pi);
                pi = NULL;
            }
#if !BB_MMU
            debug_printf_parse("as_string1 '%s'\n", ctx.as_string.data);
            if (pstring)
                *pstring = ctx.as_string.data;
            else
                o_free_unsafe(&ctx.as_string);
#endif
            debug_leave();
            debug_printf_parse("parse_stream return %p\n", pi);
            return pi;
        }
        nommu_addchr(&ctx.as_string, ch);

        next = '\0';
        if (ch != '\n')
            next = i_peek(input);

        is_special = "{}<>;&|()#'" /* special outside of "str" */
                "\\$\"" IF_HUSH_TICK("`"); /* always special */
        /* Are { and } special here? */
        if (ctx.command->argv /* word [word]{... - non-special */
         || dest.length       /* word{... - non-special */
         || dest.has_quoted_part     /* ""{... - non-special */
         || (next != ';'             /* }; - special */
            && next != ')'           /* }) - special */
            && next != '&'           /* }& and }&& ... - special */
            && next != '|'           /* }|| ... - special */
            && !strchr(defifs, next) /* {word - non-special */
            )
        ) {
            /* They are not special, skip "{}" */
            is_special += 2;
        }
        is_special = strchr(is_special, ch);
        is_blank = strchr(defifs, ch);

        if (!is_special && !is_blank) { /* ordinary char */
 ordinary_char:
            o_addQchr(&dest, ch);
            if ((dest.o_assignment == MAYBE_ASSIGNMENT
                || dest.o_assignment == WORD_IS_KEYWORD)
             && ch == '='
             && is_well_formed_var_name(dest.data, '=')
            ) {
                dest.o_assignment = DEFINITELY_ASSIGNMENT;
                debug_printf_parse("dest.o_assignment='%s'\n", assignment_flag[dest.o_assignment]);
            }
            continue;
        }

        if (is_blank) {
            if (done_word(&dest, &ctx)) {
                goto parse_error;
            }
            if (ch == '\n') {
                /* Is this a case when newline is simply ignored?
                 * Some examples:
                 * "cmd | <newline> cmd ..."
                 * "case ... in <newline> word) ..."
                 */
                if (IS_NULL_CMD(ctx.command)
                 && dest.length == 0 && !dest.has_quoted_part
                ) {
                    /* This newline can be ignored. But...
                     * Without check #1, interactive shell
                     * ignores even bare <newline>,
                     * and shows the continuation prompt:
                     * ps1_prompt$ <enter>
                     * ps2> _   <=== wrong, should be ps1
                     * Without check #2, "cmd & <newline>"
                     * is similarly mistreated.
                     * (BTW, this makes "cmd & cmd"
                     * and "cmd && cmd" non-orthogonal.
                     * Really, ask yourself, why
                     * "cmd && <newline>" doesn't start
                     * cmd but waits for more input?
                     * No reason...)
                     */
                    struct pipe *pi = ctx.list_head;
                    if (pi->num_cmds != 0       /* check #1 */
                     && pi->followup != PIPE_BG /* check #2 */
                    ) {
                        continue;
                    }
                }
                /* Treat newline as a command separator. */
                done_pipe(&ctx, PIPE_SEQ);
                debug_printf_parse("heredoc_cnt:%d\n", heredoc_cnt);
                if (heredoc_cnt) {
                    if (fetch_heredocs(heredoc_cnt, &ctx, input)) {
                        goto parse_error;
                    }
                    heredoc_cnt = 0;
                }
                dest.o_assignment = MAYBE_ASSIGNMENT;
                debug_printf_parse("dest.o_assignment='%s'\n", assignment_flag[dest.o_assignment]);
                ch = ';';
                /* note: if (is_blank) continue;
                 * will still trigger for us */
            }
        }

        /* "cmd}" or "cmd }..." without semicolon or &:
         * } is an ordinary char in this case, even inside { cmd; }
         * Pathological example: { ""}; } should exec "}" cmd
         */
        if (ch == '}') {
            if (!IS_NULL_CMD(ctx.command) /* cmd } */
             || dest.length != 0 /* word} */
             || dest.has_quoted_part    /* ""} */
            ) {
                goto ordinary_char;
            }
            if (!IS_NULL_PIPE(ctx.pipe)) /* cmd | } */
                goto skip_end_trigger;
            /* else: } does terminate a group */
        }

        if (end_trigger && end_trigger == ch
         && (ch != ';' || heredoc_cnt == 0)
#if ENABLE_HUSH_CASE
         && (ch != ')'
            || ctx.ctx_res_w != RES_MATCH
            || (!dest.has_quoted_part && strcmp(dest.data, "esac") == 0)
            )
#endif
        ) {
            if (heredoc_cnt) {
                /* This is technically valid:
                 * { cat <<HERE; }; echo Ok
                 * heredoc
                 * heredoc
                 * HERE
                 * but we don't support this.
                 * We require heredoc to be in enclosing {}/(),
                 * if any.
                 */
                syntax_error_unterm_str("here document");
                goto parse_error;
            }
            if (done_word(&dest, &ctx)) {
                goto parse_error;
            }
            done_pipe(&ctx, PIPE_SEQ);
            dest.o_assignment = MAYBE_ASSIGNMENT;
            debug_printf_parse("dest.o_assignment='%s'\n", assignment_flag[dest.o_assignment]);
            /* Do we sit outside of any if's, loops or case's? */
            if (!HAS_KEYWORDS
            IF_HAS_KEYWORDS(|| (ctx.ctx_res_w == RES_NONE && ctx.old_flag == 0))
            ) {
                o_free(&dest);
#if !BB_MMU
                debug_printf_parse("as_string2 '%s'\n", ctx.as_string.data);
                if (pstring)
                    *pstring = ctx.as_string.data;
                else
                    o_free_unsafe(&ctx.as_string);
#endif
                debug_leave();
                debug_printf_parse("parse_stream return %p: "
                        "end_trigger char found\n",
                        ctx.list_head);
                return ctx.list_head;
            }
        }
 skip_end_trigger:
        if (is_blank)
            continue;

        /* Catch <, > before deciding whether this word is
         * an assignment. a=1 2>z b=2: b=2 is still assignment */
        switch (ch) {
        case '>':
            redir_fd = redirect_opt_num(&dest);
            if (done_word(&dest, &ctx)) {
                goto parse_error;
            }
            redir_style = REDIRECT_OVERWRITE;
            if (next == '>') {
                redir_style = REDIRECT_APPEND;
                ch = i_getch(input);
                nommu_addchr(&ctx.as_string, ch);
            }
#if 0
            else if (next == '(') {
                syntax_error(">(process) not supported");
                goto parse_error;
            }
#endif
            if (parse_redirect(&ctx, redir_fd, redir_style, input))
                goto parse_error;
            continue; /* back to top of while (1) */
        case '<':
            redir_fd = redirect_opt_num(&dest);
            if (done_word(&dest, &ctx)) {
                goto parse_error;
            }
            redir_style = REDIRECT_INPUT;
            if (next == '<') {
                redir_style = REDIRECT_HEREDOC;
                heredoc_cnt++;
                debug_printf_parse("++heredoc_cnt=%d\n", heredoc_cnt);
                ch = i_getch(input);
                nommu_addchr(&ctx.as_string, ch);
            } else if (next == '>') {
                redir_style = REDIRECT_IO;
                ch = i_getch(input);
                nommu_addchr(&ctx.as_string, ch);
            }
#if 0
            else if (next == '(') {
                syntax_error("<(process) not supported");
                goto parse_error;
            }
#endif
            if (parse_redirect(&ctx, redir_fd, redir_style, input))
                goto parse_error;
            continue; /* back to top of while (1) */
        case '#':
            if (dest.length == 0 && !dest.has_quoted_part) {
                /* skip "#comment" */
                while (1) {
                    ch = i_peek(input);
                    if (ch == EOF || ch == '\n')
                        break;
                    i_getch(input);
                    /* note: we do not add it to &ctx.as_string */
                }
                nommu_addchr(&ctx.as_string, '\n');
                continue; /* back to top of while (1) */
            }
            break;
        case '\\':
            if (next == '\n') {
                /* It's "\<newline>" */
#if !BB_MMU
                /* Remove trailing '\' from ctx.as_string */
                ctx.as_string.data[--ctx.as_string.length] = '\0';
#endif
                ch = i_getch(input); /* eat it */
                continue; /* back to top of while (1) */
            }
            break;
        }

        if (dest.o_assignment == MAYBE_ASSIGNMENT
         /* check that we are not in word in "a=1 2>word b=1": */
         && !ctx.pending_redirect
        ) {
            /* ch is a special char and thus this word
             * cannot be an assignment */
            dest.o_assignment = NOT_ASSIGNMENT;
            debug_printf_parse("dest.o_assignment='%s'\n", assignment_flag[dest.o_assignment]);
        }

        /* Note: nommu_addchr(&ctx.as_string, ch) is already done */

        switch (ch) {
        case '#': /* non-comment #: "echo a#b" etc */
            o_addQchr(&dest, ch);
            break;
        case '\\':
            if (next == EOF) {
                syntax_error("\\<eof>");
                xfunc_die();
            }
            ch = i_getch(input);
            /* note: ch != '\n' (that case does not reach this place) */
            o_addchr(&dest, '\\');
            /*nommu_addchr(&ctx.as_string, '\\'); - already done */
            o_addchr(&dest, ch);
            nommu_addchr(&ctx.as_string, ch);
            /* Example: echo Hello \2>file
             * we need to know that word 2 is quoted */
            dest.has_quoted_part = 1;
            break;
        case '$':
            if (!parse_dollar(&ctx.as_string, &dest, input, /*quote_mask:*/ 0)) {
                debug_printf_parse("parse_stream parse error: "
                    "parse_dollar returned 0 (error)\n");
                goto parse_error;
            }
            break;
        case '\'':
            dest.has_quoted_part = 1;
            if (next == '\'' && !ctx.pending_redirect) {
 insert_empty_quoted_str_marker:
                nommu_addchr(&ctx.as_string, next);
                i_getch(input); /* eat second ' */
                o_addchr(&dest, SPECIAL_VAR_SYMBOL);
                o_addchr(&dest, SPECIAL_VAR_SYMBOL);
            } else {
                while (1) {
                    ch = i_getch(input);
                    if (ch == EOF) {
                        syntax_error_unterm_ch('\'');
                        goto parse_error;
                    }
                    nommu_addchr(&ctx.as_string, ch);
                    if (ch == '\'')
                        break;
                    o_addqchr(&dest, ch);
                }
            }
            break;
        case '"':
            dest.has_quoted_part = 1;
            if (next == '"' && !ctx.pending_redirect)
                goto insert_empty_quoted_str_marker;
            if (dest.o_assignment == NOT_ASSIGNMENT)
                dest.o_expflags |= EXP_FLAG_ESC_GLOB_CHARS;
            if (!encode_string(&ctx.as_string, &dest, input, '"', /*process_bkslash:*/ 1))
                goto parse_error;
            dest.o_expflags &= ~EXP_FLAG_ESC_GLOB_CHARS;
            break;
#if ENABLE_HUSH_TICK
        case '`': {
            USE_FOR_NOMMU(unsigned pos;)

            o_addchr(&dest, SPECIAL_VAR_SYMBOL);
            o_addchr(&dest, '`');
            USE_FOR_NOMMU(pos = dest.length;)
            if (!add_till_backquote(&dest, input, /*in_dquote:*/ 0))
                goto parse_error;
# if !BB_MMU
            o_addstr(&ctx.as_string, dest.data + pos);
            o_addchr(&ctx.as_string, '`');
# endif
            o_addchr(&dest, SPECIAL_VAR_SYMBOL);
            //debug_printf_subst("SUBST RES3 '%s'\n", dest.data + pos);
            break;
        }
#endif
        case ';':
#if ENABLE_HUSH_CASE
 case_semi:
#endif
            if (done_word(&dest, &ctx)) {
                goto parse_error;
            }
            done_pipe(&ctx, PIPE_SEQ);
#if ENABLE_HUSH_CASE
            /* Eat multiple semicolons, detect
             * whether it means something special */
            while (1) {
                ch = i_peek(input);
                if (ch != ';')
                    break;
                ch = i_getch(input);
                nommu_addchr(&ctx.as_string, ch);
                if (ctx.ctx_res_w == RES_CASE_BODY) {
                    ctx.ctx_dsemicolon = 1;
                    ctx.ctx_res_w = RES_MATCH;
                    break;
                }
            }
#endif
 new_cmd:
            /* We just finished a cmd. New one may start
             * with an assignment */
            dest.o_assignment = MAYBE_ASSIGNMENT;
            debug_printf_parse("dest.o_assignment='%s'\n", assignment_flag[dest.o_assignment]);
            break;
        case '&':
            if (done_word(&dest, &ctx)) {
                goto parse_error;
            }
            if (next == '&') {
                ch = i_getch(input);
                nommu_addchr(&ctx.as_string, ch);
                done_pipe(&ctx, PIPE_AND);
            } else {
                done_pipe(&ctx, PIPE_BG);
            }
            goto new_cmd;
        case '|':
            if (done_word(&dest, &ctx)) {
                goto parse_error;
            }
#if ENABLE_HUSH_CASE
            if (ctx.ctx_res_w == RES_MATCH)
                break; /* we are in case's "word | word)" */
#endif
            if (next == '|') { /* || */
                ch = i_getch(input);
                nommu_addchr(&ctx.as_string, ch);
                done_pipe(&ctx, PIPE_OR);
            } else {
                /* we could pick up a file descriptor choice here
                 * with redirect_opt_num(), but bash doesn't do it.
                 * "echo foo 2| cat" yields "foo 2". */
                done_command(&ctx);
            }
            goto new_cmd;
        case '(':
#if ENABLE_HUSH_CASE
            /* "case... in [(]word)..." - skip '(' */
            if (ctx.ctx_res_w == RES_MATCH
             && ctx.command->argv == NULL /* not (word|(... */
             && dest.length == 0 /* not word(... */
             && dest.has_quoted_part == 0 /* not ""(... */
            ) {
                continue;
            }
#endif
        case '{':
            if (parse_group(&dest, &ctx, input, ch) != 0) {
                goto parse_error;
            }
            goto new_cmd;
        case ')':
#if ENABLE_HUSH_CASE
            if (ctx.ctx_res_w == RES_MATCH)
                goto case_semi;
#endif
        case '}':
            /* proper use of this character is caught by end_trigger:
             * if we see {, we call parse_group(..., end_trigger='}')
             * and it will match } earlier (not here). */
            syntax_error_unexpected_ch(ch);
            goto parse_error;
        default:
            if (HUSH_DEBUG)
                bb_error_msg_and_die("BUG: unexpected %c\n", ch);
        }
    } /* while (1) */

 parse_error:
    {
        struct parse_context *pctx;
        IF_HAS_KEYWORDS(struct parse_context *p2;)

        /* Clean up allocated tree.
         * Sample for finding leaks on syntax error recovery path.
         * Run it from interactive shell, watch pmap `pidof hush`.
         * while if false; then false; fi; do break; fi
         * Samples to catch leaks at execution:
         * while if (true | {true;}); then echo ok; fi; do break; done
         * while if (true | {true;}); then echo ok; fi; do (if echo ok; break; then :; fi) | cat; break; done
         */
        pctx = &ctx;
        do {
            /* Update pipe/command counts,
             * otherwise freeing may miss some */
            done_pipe(pctx, PIPE_SEQ);
            debug_printf_clean("freeing list %p from ctx %p\n",
                    pctx->list_head, pctx);
            debug_print_tree(pctx->list_head, 0);
            free_pipe_list(pctx->list_head);
            debug_printf_clean("freed list %p\n", pctx->list_head);
#if !BB_MMU
            o_free_unsafe(&pctx->as_string);
#endif
            IF_HAS_KEYWORDS(p2 = pctx->stack;)
            if (pctx != &ctx) {
                free(pctx);
            }
            IF_HAS_KEYWORDS(pctx = p2;)
        } while (HAS_KEYWORDS && pctx);

        o_free(&dest);
        G.last_exitcode = 1;
#if !BB_MMU
        if (pstring)
            *pstring = NULL;
#endif
        debug_leave();
        return ERR_PTR;
    }
}


/*** Execution routines ***/

/* Expansion can recurse, need forward decls: */
#if !ENABLE_HUSH_BASH_COMPAT
/* only ${var/pattern/repl} (its pattern part) needs additional mode */
#define expand_string_to_string(str, do_unbackslash) \
    expand_string_to_string(str)
#endif
static char *expand_string_to_string(const char *str, int do_unbackslash);
#if ENABLE_HUSH_TICK
static int process_command_subs(o_string *dest, const char *s);
#endif

/* expand_strvec_to_strvec() takes a list of strings, expands
 * all variable references within and returns a pointer to
 * a list of expanded strings, possibly with larger number
 * of strings. (Think VAR="a b"; echo $VAR).
 * This new list is allocated as a single malloc block.
 * NULL-terminated list of char* pointers is at the beginning of it,
 * followed by strings themselves.
 * Caller can deallocate entire list by single free(list). */

/* A horde of its helpers come first: */

static void o_addblock_duplicate_backslash(o_string *o, const char *str, int len)
{
    while (--len >= 0) {
        char c = *str++;

#if ENABLE_HUSH_BRACE_EXPANSION
        if (c == '{' || c == '}') {
            /* { -> \{, } -> \} */
            o_addchr(o, '\\');
            /* And now we want to add { or } and continue:
             *  o_addchr(o, c);
             *  continue;
             * luckily, just falling throught achieves this.
             */
        }
#endif
        o_addchr(o, c);
        if (c == '\\') {
            /* \z -> \\\z; \<eol> -> \\<eol> */
            o_addchr(o, '\\');
            if (len) {
                len--;
                o_addchr(o, '\\');
                o_addchr(o, *str++);
            }
        }
    }
}

/* Store given string, finalizing the word and starting new one whenever
 * we encounter IFS char(s). This is used for expanding variable values.
 * End-of-string does NOT finalize word: think about 'echo -$VAR-'.
 * Return in *ended_with_ifs:
 * 1 - ended with IFS char, else 0 (this includes case of empty str).
 */
static int expand_on_ifs(int *ended_with_ifs, o_string *output, int n, const char *str)
{
    int last_is_ifs = 0;

    while (1) {
        int word_len;

        if (!*str)  /* EOL - do not finalize word */
            break;
        word_len = strcspn(str, G.ifs);
        if (word_len) {
            /* We have WORD_LEN leading non-IFS chars */
            if (!(output->o_expflags & EXP_FLAG_GLOB)) {
                o_addblock(output, str, word_len);
            } else {
                /* Protect backslashes against globbing up :)
                 * Example: "v='\*'; echo b$v" prints "b\*"
                 * (and does not try to glob on "*")
                 */
                o_addblock_duplicate_backslash(output, str, word_len);
                /*/ Why can't we do it easier? */
                /*o_addblock(output, str, word_len); - WRONG: "v='\*'; echo Z$v" prints "Z*" instead of "Z\*" */
                /*o_addqblock(output, str, word_len); - WRONG: "v='*'; echo Z$v" prints "Z*" instead of Z* files */
            }
            last_is_ifs = 0;
            str += word_len;
            if (!*str)  /* EOL - do not finalize word */
                break;
        }

        /* We know str here points to at least one IFS char */
        last_is_ifs = 1;
        str += strspn(str, G.ifs); /* skip IFS chars */
        if (!*str)  /* EOL - do not finalize word */
            break;

        /* Start new word... but not always! */
        /* Case "v=' a'; echo ''$v": we do need to finalize empty word: */
        if (output->has_quoted_part
        /* Case "v=' a'; echo $v":
         * here nothing precedes the space in $v expansion,
         * therefore we should not finish the word
         * (IOW: if there *is* word to finalize, only then do it):
         */
         || (n > 0 && output->data[output->length - 1])
        ) {
            o_addchr(output, '\0');
            debug_print_list("expand_on_ifs", output, n);
            n = o_save_ptr(output, n);
        }
    }

    if (ended_with_ifs)
        *ended_with_ifs = last_is_ifs;
    debug_print_list("expand_on_ifs[1]", output, n);
    return n;
}

/* Helper to expand $((...)) and heredoc body. These act as if
 * they are in double quotes, with the exception that they are not :).
 * Just the rules are similar: "expand only $var and `cmd`"
 *
 * Returns malloced string.
 * As an optimization, we return NULL if expansion is not needed.
 */
#if !ENABLE_HUSH_BASH_COMPAT
/* only ${var/pattern/repl} (its pattern part) needs additional mode */
#define encode_then_expand_string(str, process_bkslash, do_unbackslash) \
    encode_then_expand_string(str)
#endif
static char *encode_then_expand_string(const char *str, int process_bkslash, int do_unbackslash)
{
    char *exp_str;
    struct in_str input;
    o_string dest = NULL_O_STRING;

    if (!strchr(str, '$')
     && !strchr(str, '\\')
#if ENABLE_HUSH_TICK
     && !strchr(str, '`')
#endif
    ) {
        return NULL;
    }

    /* We need to expand. Example:
     * echo $(($a + `echo 1`)) $((1 + $((2)) ))
     */
    setup_string_in_str(&input, str);
    encode_string(NULL, &dest, &input, EOF, process_bkslash);
//TODO: error check (encode_string returns 0 on error)?
    //bb_error_msg("'%s' -> '%s'", str, dest.data);
    exp_str = expand_string_to_string(dest.data, /*unbackslash:*/ do_unbackslash);
    //bb_error_msg("'%s' -> '%s'", dest.data, exp_str);
    o_free_unsafe(&dest);
    return exp_str;
}

#if ENABLE_SH_MATH_SUPPORT
static arith_t expand_and_evaluate_arith(const char *arg, const char **errmsg_p)
{
    arith_state_t math_state;
    arith_t res;
    char *exp_str;

    math_state.lookupvar = get_local_var_value;
    math_state.setvar = set_local_var_from_halves;
    //math_state.endofname = endofname;
    exp_str = encode_then_expand_string(arg, /*process_bkslash:*/ 1, /*unbackslash:*/ 1);
    res = arith(&math_state, exp_str ? exp_str : arg);
    free(exp_str);
    if (errmsg_p)
        *errmsg_p = math_state.errmsg;
    if (math_state.errmsg)
        die_if_script(math_state.errmsg);
    return res;
}
#endif

#if ENABLE_HUSH_BASH_COMPAT
/* ${var/[/]pattern[/repl]} helpers */
static char *strstr_pattern(char *val, const char *pattern, int *size)
{
    while (1) {
        char *end = scan_and_match(val, pattern, SCAN_MOVE_FROM_RIGHT + SCAN_MATCH_LEFT_HALF);
        debug_printf_varexp("val:'%s' pattern:'%s' end:'%s'\n", val, pattern, end);
        if (end) {
            *size = end - val;
            return val;
        }
        if (*val == '\0')
            return NULL;
        /* Optimization: if "*pat" did not match the start of "string",
         * we know that "tring", "ring" etc will not match too:
         */
        if (pattern[0] == '*')
            return NULL;
        val++;
    }
}
static char *replace_pattern(char *val, const char *pattern, const char *repl, char exp_op)
{
    char *result = NULL;
    unsigned res_len = 0;
    unsigned repl_len = strlen(repl);

    while (1) {
        int size;
        char *s = strstr_pattern(val, pattern, &size);
        if (!s)
            break;

        result = xrealloc(result, res_len + (s - val) + repl_len + 1);
        memcpy(result + res_len, val, s - val);
        res_len += s - val;
        strcpy(result + res_len, repl);
        res_len += repl_len;
        debug_printf_varexp("val:'%s' s:'%s' result:'%s'\n", val, s, result);

        val = s + size;
        if (exp_op == '/')
            break;
    }
    if (val[0] && result) {
        result = xrealloc(result, res_len + strlen(val) + 1);
        strcpy(result + res_len, val);
        debug_printf_varexp("val:'%s' result:'%s'\n", val, result);
    }
    debug_printf_varexp("result:'%s'\n", result);
    return result;
}
#endif

/* Helper:
 * Handles <SPECIAL_VAR_SYMBOL>varname...<SPECIAL_VAR_SYMBOL> construct.
 */
static NOINLINE const char *expand_one_var(char **to_be_freed_pp, char *arg, char **pp)
{
    const char *val = NULL;
    char *to_be_freed = NULL;
    char *p = *pp;
    char *var;
    char first_char;
    char exp_op;
    char exp_save = exp_save; /* for compiler */
    char *exp_saveptr; /* points to expansion operator */
    char *exp_word = exp_word; /* for compiler */
    char arg0;

    *p = '\0'; /* replace trailing SPECIAL_VAR_SYMBOL */
    var = arg;
    exp_saveptr = arg[1] ? strchr(VAR_ENCODED_SUBST_OPS, arg[1]) : NULL;
    arg0 = arg[0];
    first_char = arg[0] = arg0 & 0x7f;
    exp_op = 0;

    if (first_char == '#'      /* ${#... */
     && arg[1] && !exp_saveptr /* not ${#} and not ${#<op_char>...} */
    ) {
        /* It must be length operator: ${#var} */
        var++;
        exp_op = 'L';
    } else {
        /* Maybe handle parameter expansion */
        if (exp_saveptr /* if 2nd char is one of expansion operators */
         && strchr(NUMERIC_SPECVARS_STR, first_char) /* 1st char is special variable */
        ) {
            /* ${?:0}, ${#[:]%0} etc */
            exp_saveptr = var + 1;
        } else {
            /* ${?}, ${var}, ${var:0}, ${var[:]%0} etc */
            exp_saveptr = var+1 + strcspn(var+1, VAR_ENCODED_SUBST_OPS);
        }
        exp_op = exp_save = *exp_saveptr;
        if (exp_op) {
            exp_word = exp_saveptr + 1;
            if (exp_op == ':') {
                exp_op = *exp_word++;
//TODO: try ${var:} and ${var:bogus} in non-bash config
                if (ENABLE_HUSH_BASH_COMPAT
                 && (!exp_op || !strchr(MINUS_PLUS_EQUAL_QUESTION, exp_op))
                ) {
                    /* oops... it's ${var:N[:M]}, not ${var:?xxx} or some such */
                    exp_op = ':';
                    exp_word--;
                }
            }
            *exp_saveptr = '\0';
        } /* else: it's not an expansion op, but bare ${var} */
    }

    /* Look up the variable in question */
    if (isdigit(var[0])) {
        /* parse_dollar should have vetted var for us */
        int n = xatoi_positive(var);
        if (n < G.global_argc)
            val = G.global_argv[n];
        /* else val remains NULL: $N with too big N */
    } else {
        switch (var[0]) {
        case '$': /* pid */
            val = utoa(G.root_pid);
            break;
        case '!': /* bg pid */
            val = G.last_bg_pid ? utoa(G.last_bg_pid) : "";
            break;
        case '?': /* exitcode */
            val = utoa(G.last_exitcode);
            break;
        case '#': /* argc */
            val = utoa(G.global_argc ? G.global_argc-1 : 0);
            break;
        default:
            val = get_local_var_value(var);
        }
    }

    /* Handle any expansions */
    if (exp_op == 'L') {
        reinit_unicode_for_hush();
        debug_printf_expand("expand: length(%s)=", val);
        val = utoa(val ? unicode_strlen(val) : 0);
        debug_printf_expand("%s\n", val);
    } else if (exp_op) {
        if (exp_op == '%' || exp_op == '#') {
            /* Standard-mandated substring removal ops:
             * ${parameter%word} - remove smallest suffix pattern
             * ${parameter%%word} - remove largest suffix pattern
             * ${parameter#word} - remove smallest prefix pattern
             * ${parameter##word} - remove largest prefix pattern
             *
             * Word is expanded to produce a glob pattern.
             * Then var's value is matched to it and matching part removed.
             */
            if (val && val[0]) {
                char *t;
                char *exp_exp_word;
                char *loc;
                unsigned scan_flags = pick_scan(exp_op, *exp_word);
                if (exp_op == *exp_word)  /* ## or %% */
                    exp_word++;
                exp_exp_word = encode_then_expand_string(exp_word, /*process_bkslash:*/ 1, /*unbackslash:*/ 1);
                if (exp_exp_word)
                    exp_word = exp_exp_word;
                /* HACK ALERT. We depend here on the fact that
                 * G.global_argv and results of utoa and get_local_var_value
                 * are actually in writable memory:
                 * scan_and_match momentarily stores NULs there. */
                t = (char*)val;
                loc = scan_and_match(t, exp_word, scan_flags);
                //bb_error_msg("op:%c str:'%s' pat:'%s' res:'%s'",
                //      exp_op, t, exp_word, loc);
                free(exp_exp_word);
                if (loc) { /* match was found */
                    if (scan_flags & SCAN_MATCH_LEFT_HALF) /* #[#] */
                        val = loc; /* take right part */
                    else /* %[%] */
                        val = to_be_freed = xstrndup(val, loc - val); /* left */
                }
            }
        }
#if ENABLE_HUSH_BASH_COMPAT
        else if (exp_op == '/' || exp_op == '\\') {
            /* It's ${var/[/]pattern[/repl]} thing.
             * Note that in encoded form it has TWO parts:
             * var/pattern<SPECIAL_VAR_SYMBOL>repl<SPECIAL_VAR_SYMBOL>
             * and if // is used, it is encoded as \:
             * var\pattern<SPECIAL_VAR_SYMBOL>repl<SPECIAL_VAR_SYMBOL>
             */
            /* Empty variable always gives nothing: */
            // "v=''; echo ${v/*/w}" prints "", not "w"
            if (val && val[0]) {
                /* pattern uses non-standard expansion.
                 * repl should be unbackslashed and globbed
                 * by the usual expansion rules:
                 * >az; >bz;
                 * v='a bz'; echo "${v/a*z/a*z}" prints "a*z"
                 * v='a bz'; echo "${v/a*z/\z}"  prints "\z"
                 * v='a bz'; echo ${v/a*z/a*z}   prints "az"
                 * v='a bz'; echo ${v/a*z/\z}    prints "z"
                 * (note that a*z _pattern_ is never globbed!)
                 */
                char *pattern, *repl, *t;
                pattern = encode_then_expand_string(exp_word, /*process_bkslash:*/ 0, /*unbackslash:*/ 0);
                if (!pattern)
                    pattern = xstrdup(exp_word);
                debug_printf_varexp("pattern:'%s'->'%s'\n", exp_word, pattern);
                *p++ = SPECIAL_VAR_SYMBOL;
                exp_word = p;
                p = strchr(p, SPECIAL_VAR_SYMBOL);
                *p = '\0';
                repl = encode_then_expand_string(exp_word, /*process_bkslash:*/ arg0 & 0x80, /*unbackslash:*/ 1);
                debug_printf_varexp("repl:'%s'->'%s'\n", exp_word, repl);
                /* HACK ALERT. We depend here on the fact that
                 * G.global_argv and results of utoa and get_local_var_value
                 * are actually in writable memory:
                 * replace_pattern momentarily stores NULs there. */
                t = (char*)val;
                to_be_freed = replace_pattern(t,
                        pattern,
                        (repl ? repl : exp_word),
                        exp_op);
                if (to_be_freed) /* at least one replace happened */
                    val = to_be_freed;
                free(pattern);
                free(repl);
            }
        }
#endif
        else if (exp_op == ':') {
#if ENABLE_HUSH_BASH_COMPAT && ENABLE_SH_MATH_SUPPORT
            /* It's ${var:N[:M]} bashism.
             * Note that in encoded form it has TWO parts:
             * var:N<SPECIAL_VAR_SYMBOL>M<SPECIAL_VAR_SYMBOL>
             */
            arith_t beg, len;
            const char *errmsg;

            beg = expand_and_evaluate_arith(exp_word, &errmsg);
            if (errmsg)
                goto arith_err;
            debug_printf_varexp("beg:'%s'=%lld\n", exp_word, (long long)beg);
            *p++ = SPECIAL_VAR_SYMBOL;
            exp_word = p;
            p = strchr(p, SPECIAL_VAR_SYMBOL);
            *p = '\0';
            len = expand_and_evaluate_arith(exp_word, &errmsg);
            if (errmsg)
                goto arith_err;
            debug_printf_varexp("len:'%s'=%lld\n", exp_word, (long long)len);
            if (len >= 0) { /* bash compat: len < 0 is illegal */
                if (beg < 0) /* bash compat */
                    beg = 0;
                debug_printf_varexp("from val:'%s'\n", val);
                if (len == 0 || !val || beg >= strlen(val)) {
 arith_err:
                    val = NULL;
                } else {
                    /* Paranoia. What if user entered 9999999999999
                     * which fits in arith_t but not int? */
                    if (len >= INT_MAX)
                        len = INT_MAX;
                    val = to_be_freed = xstrndup(val + beg, len);
                }
                debug_printf_varexp("val:'%s'\n", val);
            } else
#endif
            {
                die_if_script("malformed ${%s:...}", var);
                val = NULL;
            }
        } else { /* one of "-=+?" */
            /* Standard-mandated substitution ops:
             * ${var?word} - indicate error if unset
             *      If var is unset, word (or a message indicating it is unset
             *      if word is null) is written to standard error
             *      and the shell exits with a non-zero exit status.
             *      Otherwise, the value of var is substituted.
             * ${var-word} - use default value
             *      If var is unset, word is substituted.
             * ${var=word} - assign and use default value
             *      If var is unset, word is assigned to var.
             *      In all cases, final value of var is substituted.
             * ${var+word} - use alternative value
             *      If var is unset, null is substituted.
             *      Otherwise, word is substituted.
             *
             * Word is subjected to tilde expansion, parameter expansion,
             * command substitution, and arithmetic expansion.
             * If word is not needed, it is not expanded.
             *
             * Colon forms (${var:-word}, ${var:=word} etc) do the same,
             * but also treat null var as if it is unset.
             */
            int use_word = (!val || ((exp_save == ':') && !val[0]));
            if (exp_op == '+')
                use_word = !use_word;
            debug_printf_expand("expand: op:%c (null:%s) test:%i\n", exp_op,
                    (exp_save == ':') ? "true" : "false", use_word);
            if (use_word) {
                to_be_freed = encode_then_expand_string(exp_word, /*process_bkslash:*/ 1, /*unbackslash:*/ 1);
                if (to_be_freed)
                    exp_word = to_be_freed;
                if (exp_op == '?') {
                    /* mimic bash message */
                    die_if_script("%s: %s",
                        var,
                        exp_word[0] ? exp_word : "parameter null or not set"
                    );
//TODO: how interactive bash aborts expansion mid-command?
                } else {
                    val = exp_word;
                }

                if (exp_op == '=') {
                    /* ${var=[word]} or ${var:=[word]} */
                    if (isdigit(var[0]) || var[0] == '#') {
                        /* mimic bash message */
                        die_if_script("$%s: cannot assign in this way", var);
                        val = NULL;
                    } else {
                        char *new_var = xasprintf("%s=%s", var, val);
                        set_local_var(new_var, /*exp:*/ 0, /*lvl:*/ 0, /*ro:*/ 0);
                    }
                }
            }
        } /* one of "-=+?" */

        *exp_saveptr = exp_save;
    } /* if (exp_op) */

    arg[0] = arg0;

    *pp = p;
    *to_be_freed_pp = to_be_freed;
    return val;
}

/* Expand all variable references in given string, adding words to list[]
 * at n, n+1,... positions. Return updated n (so that list[n] is next one
 * to be filled). This routine is extremely tricky: has to deal with
 * variables/parameters with whitespace, $* and $@, and constructs like
 * 'echo -$*-'. If you play here, you must run testsuite afterwards! */
static NOINLINE int expand_vars_to_list(o_string *output, int n, char *arg)
{
    /* output->o_expflags & EXP_FLAG_SINGLEWORD (0x80) if we are in
     * expansion of right-hand side of assignment == 1-element expand.
     */
    char cant_be_null = 0; /* only bit 0x80 matters */
    int ended_in_ifs = 0;  /* did last unquoted expansion end with IFS chars? */
    char *p;

    debug_printf_expand("expand_vars_to_list: arg:'%s' singleword:%x\n", arg,
            !!(output->o_expflags & EXP_FLAG_SINGLEWORD));
    debug_print_list("expand_vars_to_list", output, n);
    n = o_save_ptr(output, n);
    debug_print_list("expand_vars_to_list[0]", output, n);

    while ((p = strchr(arg, SPECIAL_VAR_SYMBOL)) != NULL) {
        char first_ch;
        char *to_be_freed = NULL;
        const char *val = NULL;
#if ENABLE_HUSH_TICK
        o_string subst_result = NULL_O_STRING;
#endif
#if ENABLE_SH_MATH_SUPPORT
        char arith_buf[sizeof(arith_t)*3 + 2];
#endif

        if (ended_in_ifs) {
            o_addchr(output, '\0');
            n = o_save_ptr(output, n);
            ended_in_ifs = 0;
        }

        o_addblock(output, arg, p - arg);
        debug_print_list("expand_vars_to_list[1]", output, n);
        arg = ++p;
        p = strchr(p, SPECIAL_VAR_SYMBOL);

        /* Fetch special var name (if it is indeed one of them)
         * and quote bit, force the bit on if singleword expansion -
         * important for not getting v=$@ expand to many words. */
        first_ch = arg[0] | (output->o_expflags & EXP_FLAG_SINGLEWORD);

        /* Is this variable quoted and thus expansion can't be null?
         * "$@" is special. Even if quoted, it can still
         * expand to nothing (not even an empty string),
         * thus it is excluded. */
        if ((first_ch & 0x7f) != '@')
            cant_be_null |= first_ch;

        switch (first_ch & 0x7f) {
        /* Highest bit in first_ch indicates that var is double-quoted */
        case '*':
        case '@': {
            int i;
            if (!G.global_argv[1])
                break;
            i = 1;
            cant_be_null |= first_ch; /* do it for "$@" _now_, when we know it's not empty */
            if (!(first_ch & 0x80)) { /* unquoted $* or $@ */
                while (G.global_argv[i]) {
                    n = expand_on_ifs(NULL, output, n, G.global_argv[i]);
                    debug_printf_expand("expand_vars_to_list: argv %d (last %d)\n", i, G.global_argc - 1);
                    if (G.global_argv[i++][0] && G.global_argv[i]) {
                        /* this argv[] is not empty and not last:
                         * put terminating NUL, start new word */
                        o_addchr(output, '\0');
                        debug_print_list("expand_vars_to_list[2]", output, n);
                        n = o_save_ptr(output, n);
                        debug_print_list("expand_vars_to_list[3]", output, n);
                    }
                }
            } else
            /* If EXP_FLAG_SINGLEWORD, we handle assignment 'a=....$@.....'
             * and in this case should treat it like '$*' - see 'else...' below */
            if (first_ch == ('@'|0x80)  /* quoted $@ */
             && !(output->o_expflags & EXP_FLAG_SINGLEWORD) /* not v="$@" case */
            ) {
                while (1) {
                    o_addQstr(output, G.global_argv[i]);
                    if (++i >= G.global_argc)
                        break;
                    o_addchr(output, '\0');
                    debug_print_list("expand_vars_to_list[4]", output, n);
                    n = o_save_ptr(output, n);
                }
            } else { /* quoted $* (or v="$@" case): add as one word */
                while (1) {
                    o_addQstr(output, G.global_argv[i]);
                    if (!G.global_argv[++i])
                        break;
                    if (G.ifs[0])
                        o_addchr(output, G.ifs[0]);
                }
                output->has_quoted_part = 1;
            }
            break;
        }
        case SPECIAL_VAR_SYMBOL: /* <SPECIAL_VAR_SYMBOL><SPECIAL_VAR_SYMBOL> */
            /* "Empty variable", used to make "" etc to not disappear */
            output->has_quoted_part = 1;
            arg++;
            cant_be_null = 0x80;
            break;
#if ENABLE_HUSH_TICK
        case '`': /* <SPECIAL_VAR_SYMBOL>`cmd<SPECIAL_VAR_SYMBOL> */
            *p = '\0'; /* replace trailing <SPECIAL_VAR_SYMBOL> */
            arg++;
            /* Can't just stuff it into output o_string,
             * expanded result may need to be globbed
             * and $IFS-splitted */
            debug_printf_subst("SUBST '%s' first_ch %x\n", arg, first_ch);
            G.last_exitcode = process_command_subs(&subst_result, arg);
            debug_printf_subst("SUBST RES:%d '%s'\n", G.last_exitcode, subst_result.data);
            val = subst_result.data;
            goto store_val;
#endif
#if ENABLE_SH_MATH_SUPPORT
        case '+': { /* <SPECIAL_VAR_SYMBOL>+cmd<SPECIAL_VAR_SYMBOL> */
            arith_t res;

            arg++; /* skip '+' */
            *p = '\0'; /* replace trailing <SPECIAL_VAR_SYMBOL> */
            debug_printf_subst("ARITH '%s' first_ch %x\n", arg, first_ch);
            res = expand_and_evaluate_arith(arg, NULL);
            debug_printf_subst("ARITH RES '"ARITH_FMT"'\n", res);
            sprintf(arith_buf, ARITH_FMT, res);
            val = arith_buf;
            break;
        }
#endif
        default:
            val = expand_one_var(&to_be_freed, arg, &p);
 IF_HUSH_TICK(store_val:)
            if (!(first_ch & 0x80)) { /* unquoted $VAR */
                debug_printf_expand("unquoted '%s', output->o_escape:%d\n", val,
                        !!(output->o_expflags & EXP_FLAG_ESC_GLOB_CHARS));
                if (val && val[0]) {
                    n = expand_on_ifs(&ended_in_ifs, output, n, val);
                    val = NULL;
                }
            } else { /* quoted $VAR, val will be appended below */
                output->has_quoted_part = 1;
                debug_printf_expand("quoted '%s', output->o_escape:%d\n", val,
                        !!(output->o_expflags & EXP_FLAG_ESC_GLOB_CHARS));
            }
            break;
        } /* switch (char after <SPECIAL_VAR_SYMBOL>) */

        if (val && val[0]) {
            o_addQstr(output, val);
        }
        free(to_be_freed);

        /* Restore NULL'ed SPECIAL_VAR_SYMBOL.
         * Do the check to avoid writing to a const string. */
        if (*p != SPECIAL_VAR_SYMBOL)
            *p = SPECIAL_VAR_SYMBOL;

#if ENABLE_HUSH_TICK
        o_free(&subst_result);
#endif
        arg = ++p;
    } /* end of "while (SPECIAL_VAR_SYMBOL is found) ..." */

    if (arg[0]) {
        if (ended_in_ifs) {
            o_addchr(output, '\0');
            n = o_save_ptr(output, n);
        }
        debug_print_list("expand_vars_to_list[a]", output, n);
        /* this part is literal, and it was already pre-quoted
         * if needed (much earlier), do not use o_addQstr here! */
        o_addstr_with_NUL(output, arg);
        debug_print_list("expand_vars_to_list[b]", output, n);
    } else if (output->length == o_get_last_ptr(output, n) /* expansion is empty */
     && !(cant_be_null & 0x80) /* and all vars were not quoted. */
    ) {
        n--;
        /* allow to reuse list[n] later without re-growth */
        output->has_empty_slot = 1;
    } else {
        o_addchr(output, '\0');
    }

    return n;
}

static char **expand_variables(char **argv, unsigned expflags)
{
    int n;
    char **list;
    o_string output = NULL_O_STRING;

    output.o_expflags = expflags;

    n = 0;
    while (*argv) {
        n = expand_vars_to_list(&output, n, *argv);
        argv++;
    }
    debug_print_list("expand_variables", &output, n);

    /* output.data (malloced in one block) gets returned in "list" */
    list = o_finalize_list(&output, n);
    debug_print_strings("expand_variables[1]", list);
    return list;
}

static char **expand_strvec_to_strvec(char **argv)
{
    return expand_variables(argv, EXP_FLAG_GLOB | EXP_FLAG_ESC_GLOB_CHARS);
}

#if ENABLE_HUSH_BASH_COMPAT
static char **expand_strvec_to_strvec_singleword_noglob(char **argv)
{
    return expand_variables(argv, EXP_FLAG_SINGLEWORD);
}
#endif

/* Used for expansion of right hand of assignments,
 * $((...)), heredocs, variable espansion parts.
 *
 * NB: should NOT do globbing!
 * "export v=/bin/c*; env | grep ^v=" outputs "v=/bin/c*"
 */
static char *expand_string_to_string(const char *str, int do_unbackslash)
{
#if !ENABLE_HUSH_BASH_COMPAT
    const int do_unbackslash = 1;
#endif
    char *argv[2], **list;

    debug_printf_expand("string_to_string<='%s'\n", str);
    /* This is generally an optimization, but it also
     * handles "", which otherwise trips over !list[0] check below.
     * (is this ever happens that we actually get str="" here?)
     */
    if (!strchr(str, SPECIAL_VAR_SYMBOL) && !strchr(str, '\\')) {
        //TODO: Can use on strings with \ too, just unbackslash() them?
        debug_printf_expand("string_to_string(fast)=>'%s'\n", str);
        return xstrdup(str);
    }

    argv[0] = (char*)str;
    argv[1] = NULL;
    list = expand_variables(argv, do_unbackslash
            ? EXP_FLAG_ESC_GLOB_CHARS | EXP_FLAG_SINGLEWORD
            : EXP_FLAG_SINGLEWORD
    );
    if (HUSH_DEBUG)
        if (!list[0] || list[1])
            bb_error_msg_and_die("BUG in varexp2");
    /* actually, just move string 2*sizeof(char*) bytes back */
    overlapping_strcpy((char*)list, list[0]);
    if (do_unbackslash)
        unbackslash((char*)list);
    debug_printf_expand("string_to_string=>'%s'\n", (char*)list);
    return (char*)list;
}

/* Used for "eval" builtin */
static char* expand_strvec_to_string(char **argv)
{
    char **list;

    list = expand_variables(argv, EXP_FLAG_SINGLEWORD);
    /* Convert all NULs to spaces */
    if (list[0]) {
        int n = 1;
        while (list[n]) {
            if (HUSH_DEBUG)
                if (list[n-1] + strlen(list[n-1]) + 1 != list[n])
                    bb_error_msg_and_die("BUG in varexp3");
            /* bash uses ' ' regardless of $IFS contents */
            list[n][-1] = ' ';
            n++;
        }
    }
    overlapping_strcpy((char*)list, list[0]);
    debug_printf_expand("strvec_to_string='%s'\n", (char*)list);
    return (char*)list;
}

static char **expand_assignments(char **argv, int count)
{
    int i;
    char **p;

    G.expanded_assignments = p = NULL;
    /* Expand assignments into one string each */
    for (i = 0; i < count; i++) {
        G.expanded_assignments = p = add_string_to_strings(p, expand_string_to_string(argv[i], /*unbackslash:*/ 1));
    }
    G.expanded_assignments = NULL;
    return p;
}


static void switch_off_special_sigs(unsigned mask)
{
    unsigned sig = 0;
    while ((mask >>= 1) != 0) {
        sig++;
        if (!(mask & 1))
            continue;
        if (G.traps) {
            if (G.traps[sig] && !G.traps[sig][0])
                /* trap is '', has to remain SIG_IGN */
                continue;
            free(G.traps[sig]);
            G.traps[sig] = NULL;
        }
        /* We are here only if no trap or trap was not '' */
        install_sighandler(sig, SIG_DFL);
    }
}

#if BB_MMU
/* never called */
void re_execute_shell(char ***to_free, const char *s,
        char *g_argv0, char **g_argv,
        char **builtin_argv) NORETURN;

static void reset_traps_to_defaults(void)
{
    /* This function is always called in a child shell
     * after fork (not vfork, NOMMU doesn't use this function).
     */
    unsigned sig;
    unsigned mask;

    /* Child shells are not interactive.
     * SIGTTIN/SIGTTOU/SIGTSTP should not have special handling.
     * Testcase: (while :; do :; done) + ^Z should background.
     * Same goes for SIGTERM, SIGHUP, SIGINT.
     */
    mask = (G.special_sig_mask & SPECIAL_INTERACTIVE_SIGS) | G_fatal_sig_mask;
    if (!G.traps && !mask)
        return; /* already no traps and no special sigs */

    /* Switch off special sigs */
    switch_off_special_sigs(mask);
#if ENABLE_HUSH_JOB
    G_fatal_sig_mask = 0;
#endif
    G.special_sig_mask &= ~SPECIAL_INTERACTIVE_SIGS;
    /* SIGQUIT,SIGCHLD and maybe SPECIAL_JOBSTOP_SIGS
     * remain set in G.special_sig_mask */

    if (!G.traps)
        return;

    /* Reset all sigs to default except ones with empty traps */
    for (sig = 0; sig < NSIG; sig++) {
        if (!G.traps[sig])
            continue; /* no trap: nothing to do */
        if (!G.traps[sig][0])
            continue; /* empty trap: has to remain SIG_IGN */
        /* sig has non-empty trap, reset it: */
        free(G.traps[sig]);
        G.traps[sig] = NULL;
        /* There is no signal for trap 0 (EXIT) */
        if (sig == 0)
            continue;
        install_sighandler(sig, pick_sighandler(sig));
    }
}

#else /* !BB_MMU */

static void re_execute_shell(char ***to_free, const char *s,
        char *g_argv0, char **g_argv,
        char **builtin_argv) NORETURN;
static void re_execute_shell(char ***to_free, const char *s,
        char *g_argv0, char **g_argv,
        char **builtin_argv)
{
# define NOMMU_HACK_FMT ("-$%x:%x:%x:%x:%x:%llx" IF_HUSH_LOOPS(":%x"))
    /* delims + 2 * (number of bytes in printed hex numbers) */
    char param_buf[sizeof(NOMMU_HACK_FMT) + 2 * (sizeof(int)*6 + sizeof(long long)*1)];
    char *heredoc_argv[4];
    struct variable *cur;
# if ENABLE_HUSH_FUNCTIONS
    struct function *funcp;
# endif
    char **argv, **pp;
    unsigned cnt;
    unsigned long long empty_trap_mask;

    if (!g_argv0) { /* heredoc */
        argv = heredoc_argv;
        argv[0] = (char *) G.argv0_for_re_execing;
        argv[1] = (char *) "-<";
        argv[2] = (char *) s;
        argv[3] = NULL;
        pp = &argv[3]; /* used as pointer to empty environment */
        goto do_exec;
    }

    cnt = 0;
    pp = builtin_argv;
    if (pp) while (*pp++)
        cnt++;

    empty_trap_mask = 0;
    if (G.traps) {
        int sig;
        for (sig = 1; sig < NSIG; sig++) {
            if (G.traps[sig] && !G.traps[sig][0])
                empty_trap_mask |= 1LL << sig;
        }
    }

    sprintf(param_buf, NOMMU_HACK_FMT
            , (unsigned) G.root_pid
            , (unsigned) G.root_ppid
            , (unsigned) G.last_bg_pid
            , (unsigned) G.last_exitcode
            , cnt
            , empty_trap_mask
            IF_HUSH_LOOPS(, G.depth_of_loop)
            );
# undef NOMMU_HACK_FMT
    /* 1:hush 2:-$<pid>:<pid>:<exitcode>:<etc...> <vars...> <funcs...>
     * 3:-c 4:<cmd> 5:<arg0> <argN...> 6:NULL
     */
    cnt += 6;
    for (cur = G.top_var; cur; cur = cur->next) {
        if (!cur->flg_export || cur->flg_read_only)
            cnt += 2;
    }
# if ENABLE_HUSH_FUNCTIONS
    for (funcp = G.top_func; funcp; funcp = funcp->next)
        cnt += 3;
# endif
    pp = g_argv;
    while (*pp++)
        cnt++;
    *to_free = argv = pp = xzalloc(sizeof(argv[0]) * cnt);
    *pp++ = (char *) G.argv0_for_re_execing;
    *pp++ = param_buf;
    for (cur = G.top_var; cur; cur = cur->next) {
        if (strcmp(cur->varstr, hush_version_str) == 0)
            continue;
        if (cur->flg_read_only) {
            *pp++ = (char *) "-R";
            *pp++ = cur->varstr;
        } else if (!cur->flg_export) {
            *pp++ = (char *) "-V";
            *pp++ = cur->varstr;
        }
    }
# if ENABLE_HUSH_FUNCTIONS
    for (funcp = G.top_func; funcp; funcp = funcp->next) {
        *pp++ = (char *) "-F";
        *pp++ = funcp->name;
        *pp++ = funcp->body_as_string;
    }
# endif
    /* We can pass activated traps here. Say, -Tnn:trap_string
     *
     * However, POSIX says that subshells reset signals with traps
     * to SIG_DFL.
     * I tested bash-3.2 and it not only does that with true subshells
     * of the form ( list ), but with any forked children shells.
     * I set trap "echo W" WINCH; and then tried:
     *
     * { echo 1; sleep 20; echo 2; } &
     * while true; do echo 1; sleep 20; echo 2; break; done &
     * true | { echo 1; sleep 20; echo 2; } | cat
     *
     * In all these cases sending SIGWINCH to the child shell
     * did not run the trap. If I add trap "echo V" WINCH;
     * _inside_ group (just before echo 1), it works.
     *
     * I conclude it means we don't need to pass active traps here.
     */
    *pp++ = (char *) "-c";
    *pp++ = (char *) s;
    if (builtin_argv) {
        while (*++builtin_argv)
            *pp++ = *builtin_argv;
        *pp++ = (char *) "";
    }
    *pp++ = g_argv0;
    while (*g_argv)
        *pp++ = *g_argv++;
    /* *pp = NULL; - is already there */
    pp = environ;

 do_exec:
    debug_printf_exec("re_execute_shell pid:%d cmd:'%s'\n", getpid(), s);
    /* Don't propagate SIG_IGN to the child */
    if (SPECIAL_JOBSTOP_SIGS != 0)
        switch_off_special_sigs(G.special_sig_mask & SPECIAL_JOBSTOP_SIGS);
    execve(bb_busybox_exec_path, argv, pp);
    /* Fallback. Useful for init=/bin/hush usage etc */
    if (argv[0][0] == '/')
        execve(argv[0], argv, pp);
    xfunc_error_retval = 127;
    bb_error_msg_and_die("can't re-execute the shell");
}
#endif  /* !BB_MMU */


static int run_and_free_list(struct pipe *pi);

/* Executing from string: eval, sh -c '...'
 *          or from file: /etc/profile, . file, sh <script>, sh (intereactive)
 * end_trigger controls how often we stop parsing
 * NUL: parse all, execute, return
 * ';': parse till ';' or newline, execute, repeat till EOF
 */
static void parse_and_run_stream(struct in_str *inp, int end_trigger)
{
    /* Why we need empty flag?
     * An obscure corner case "false; ``; echo $?":
     * empty command in `` should still set $? to 0.
     * But we can't just set $? to 0 at the start,
     * this breaks "false; echo `echo $?`" case.
     */
    bool empty = 1;
    while (1) {
        struct pipe *pipe_list;

#if ENABLE_HUSH_INTERACTIVE
        if (end_trigger == ';')
            inp->promptmode = 0; /* PS1 */
#endif
        pipe_list = parse_stream(NULL, inp, end_trigger);
        if (!pipe_list || pipe_list == ERR_PTR) { /* EOF/error */
            /* If we are in "big" script
             * (not in `cmd` or something similar)...
             */
            if (pipe_list == ERR_PTR && end_trigger == ';') {
                /* Discard cached input (rest of line) */
                int ch = inp->last_char;
                while (ch != EOF && ch != '\n') {
                    //bb_error_msg("Discarded:'%c'", ch);
                    ch = i_getch(inp);
                }
                /* Force prompt */
                inp->p = NULL;
                /* This stream isn't empty */
                empty = 0;
                continue;
            }
            if (!pipe_list && empty)
                G.last_exitcode = 0;
            break;
        }
        debug_print_tree(pipe_list, 0);
        debug_printf_exec("parse_and_run_stream: run_and_free_list\n");
        run_and_free_list(pipe_list);
        empty = 0;
#if ENABLE_HUSH_FUNCTIONS
        if (G.flag_return_in_progress == 1)
            break;
#endif
    }
}

static void parse_and_run_string(const char *s)
{
    struct in_str input;
    setup_string_in_str(&input, s);
    parse_and_run_stream(&input, '\0');
}

static void parse_and_run_file(FILE *f)
{
    struct in_str input;
    setup_file_in_str(&input, f);
    parse_and_run_stream(&input, ';');
}

#if ENABLE_HUSH_TICK
static FILE *generate_stream_from_string(const char *s, pid_t *pid_p)
{
    pid_t pid;
    int channel[2];
# if !BB_MMU
    char **to_free = NULL;
# endif

    xpipe(channel);
    pid = BB_MMU ? xfork() : xvfork();
    if (pid == 0) { /* child */
        disable_restore_tty_pgrp_on_exit();
        /* Process substitution is not considered to be usual
         * 'command execution'.
         * SUSv3 says ctrl-Z should be ignored, ctrl-C should not.
         */
        bb_signals(0
            + (1 << SIGTSTP)
            + (1 << SIGTTIN)
            + (1 << SIGTTOU)
            , SIG_IGN);
        CLEAR_RANDOM_T(&G.random_gen); /* or else $RANDOM repeats in child */
        close(channel[0]); /* NB: close _first_, then move fd! */
        xmove_fd(channel[1], 1);
        /* Prevent it from trying to handle ctrl-z etc */
        IF_HUSH_JOB(G.run_list_level = 1;)
        /* Awful hack for `trap` or $(trap).
         *
         * http://www.opengroup.org/onlinepubs/009695399/utilities/trap.html
         * contains an example where "trap" is executed in a subshell:
         *
         * save_traps=$(trap)
         * ...
         * eval "$save_traps"
         *
         * Standard does not say that "trap" in subshell shall print
         * parent shell's traps. It only says that its output
         * must have suitable form, but then, in the above example
         * (which is not supposed to be normative), it implies that.
         *
         * bash (and probably other shell) does implement it
         * (traps are reset to defaults, but "trap" still shows them),
         * but as a result, "trap" logic is hopelessly messed up:
         *
         * # trap
         * trap -- 'echo Ho' SIGWINCH  <--- we have a handler
         * # (trap)        <--- trap is in subshell - no output (correct, traps are reset)
         * # true | trap   <--- trap is in subshell - no output (ditto)
         * # echo `true | trap`    <--- in subshell - output (but traps are reset!)
         * trap -- 'echo Ho' SIGWINCH
         * # echo `(trap)`         <--- in subshell in subshell - output
         * trap -- 'echo Ho' SIGWINCH
         * # echo `true | (trap)`  <--- in subshell in subshell in subshell - output!
         * trap -- 'echo Ho' SIGWINCH
         *
         * The rules when to forget and when to not forget traps
         * get really complex and nonsensical.
         *
         * Our solution: ONLY bare $(trap) or `trap` is special.
         */
        s = skip_whitespace(s);
        if (is_prefixed_with(s, "trap")
         && skip_whitespace(s + 4)[0] == '\0'
        ) {
            static const char *const argv[] = { NULL, NULL };
            builtin_trap((char**)argv);
            fflush_all(); /* important */
            _exit(0);
        }
# if BB_MMU
        reset_traps_to_defaults();
        parse_and_run_string(s);
        _exit(G.last_exitcode);
# else
    /* We re-execute after vfork on NOMMU. This makes this script safe:
     * yes "0123456789012345678901234567890" | dd bs=32 count=64k >BIG
     * huge=`cat BIG` # was blocking here forever
     * echo OK
     */
        re_execute_shell(&to_free,
                s,
                G.global_argv[0],
                G.global_argv + 1,
                NULL);
# endif
    }

    /* parent */
    *pid_p = pid;
# if ENABLE_HUSH_FAST
    G.count_SIGCHLD++;
//bb_error_msg("[%d] fork in generate_stream_from_string:"
//      " G.count_SIGCHLD:%d G.handled_SIGCHLD:%d",
//      getpid(), G.count_SIGCHLD, G.handled_SIGCHLD);
# endif
    enable_restore_tty_pgrp_on_exit();
# if !BB_MMU
    free(to_free);
# endif
    close(channel[1]);
    close_on_exec_on(channel[0]);
    return xfdopen_for_read(channel[0]);
}

/* Return code is exit status of the process that is run. */
static int process_command_subs(o_string *dest, const char *s)
{
    FILE *fp;
    struct in_str pipe_str;
    pid_t pid;
    int status, ch, eol_cnt;

    fp = generate_stream_from_string(s, &pid);

    /* Now send results of command back into original context */
    setup_file_in_str(&pipe_str, fp);
    eol_cnt = 0;
    while ((ch = i_getch(&pipe_str)) != EOF) {
        if (ch == '\n') {
            eol_cnt++;
            continue;
        }
        while (eol_cnt) {
            o_addchr(dest, '\n');
            eol_cnt--;
        }
        o_addQchr(dest, ch);
    }

    debug_printf("done reading from `cmd` pipe, closing it\n");
    fclose(fp);
    /* We need to extract exitcode. Test case
     * "true; echo `sleep 1; false` $?"
     * should print 1 */
    safe_waitpid(pid, &status, 0);
    debug_printf("child exited. returning its exitcode:%d\n", WEXITSTATUS(status));
    return WEXITSTATUS(status);
}
#endif /* ENABLE_HUSH_TICK */


static void setup_heredoc(struct redir_struct *redir)
{
    struct fd_pair pair;
    pid_t pid;
    int len, written;
    /* the _body_ of heredoc (misleading field name) */
    const char *heredoc = redir->rd_filename;
    char *expanded;
#if !BB_MMU
    char **to_free;
#endif

    expanded = NULL;
    if (!(redir->rd_dup & HEREDOC_QUOTED)) {
        expanded = encode_then_expand_string(heredoc, /*process_bkslash:*/ 1, /*unbackslash:*/ 1);
        if (expanded)
            heredoc = expanded;
    }
    len = strlen(heredoc);

    close(redir->rd_fd); /* often saves dup2+close in xmove_fd */
    xpiped_pair(pair);
    xmove_fd(pair.rd, redir->rd_fd);

    /* Try writing without forking. Newer kernels have
     * dynamically growing pipes. Must use non-blocking write! */
    ndelay_on(pair.wr);
    while (1) {
        written = write(pair.wr, heredoc, len);
        if (written <= 0)
            break;
        len -= written;
        if (len == 0) {
            close(pair.wr);
            free(expanded);
            return;
        }
        heredoc += written;
    }
    ndelay_off(pair.wr);

    /* Okay, pipe buffer was not big enough */
    /* Note: we must not create a stray child (bastard? :)
     * for the unsuspecting parent process. Child creates a grandchild
     * and exits before parent execs the process which consumes heredoc
     * (that exec happens after we return from this function) */
#if !BB_MMU
    to_free = NULL;
#endif
    pid = xvfork();
    if (pid == 0) {
        /* child */
        disable_restore_tty_pgrp_on_exit();
        pid = BB_MMU ? xfork() : xvfork();
        if (pid != 0)
            _exit(0);
        /* grandchild */
        close(redir->rd_fd); /* read side of the pipe */
#if BB_MMU
        full_write(pair.wr, heredoc, len); /* may loop or block */
        _exit(0);
#else
        /* Delegate blocking writes to another process */
        xmove_fd(pair.wr, STDOUT_FILENO);
        re_execute_shell(&to_free, heredoc, NULL, NULL, NULL);
#endif
    }
    /* parent */
#if ENABLE_HUSH_FAST
    G.count_SIGCHLD++;
//bb_error_msg("[%d] fork in setup_heredoc: G.count_SIGCHLD:%d G.handled_SIGCHLD:%d", getpid(), G.count_SIGCHLD, G.handled_SIGCHLD);
#endif
    enable_restore_tty_pgrp_on_exit();
#if !BB_MMU
    free(to_free);
#endif
    close(pair.wr);
    free(expanded);
    wait(NULL); /* wait till child has died */
}

/* squirrel != NULL means we squirrel away copies of stdin, stdout,
 * and stderr if they are redirected. */
static int setup_redirects(struct command *prog, int squirrel[])
{
    int openfd, mode;
    struct redir_struct *redir;

    for (redir = prog->redirects; redir; redir = redir->next) {
        if (redir->rd_type == REDIRECT_HEREDOC2) {
            /* rd_fd<<HERE case */
            if (squirrel && redir->rd_fd < 3
             && squirrel[redir->rd_fd] < 0
            ) {
                squirrel[redir->rd_fd] = dup(redir->rd_fd);
            }
            /* for REDIRECT_HEREDOC2, rd_filename holds _contents_
             * of the heredoc */
            debug_printf_parse("set heredoc '%s'\n",
                    redir->rd_filename);
            setup_heredoc(redir);
            continue;
        }

        if (redir->rd_dup == REDIRFD_TO_FILE) {
            /* rd_fd<*>file case (<*> is <,>,>>,<>) */
            char *p;
            if (redir->rd_filename == NULL) {
                /* Something went wrong in the parse.
                 * Pretend it didn't happen */
                bb_error_msg("bug in redirect parse");
                continue;
            }
            mode = redir_table[redir->rd_type].mode;
            p = expand_string_to_string(redir->rd_filename, /*unbackslash:*/ 1);
            openfd = open_or_warn(p, mode);
            free(p);
            if (openfd < 0) {
            /* this could get lost if stderr has been redirected, but
             * bash and ash both lose it as well (though zsh doesn't!) */
//what the above comment tries to say?
                return 1;
            }
        } else {
            /* rd_fd<*>rd_dup or rd_fd<*>- cases */
            openfd = redir->rd_dup;
        }

        if (openfd != redir->rd_fd) {
            if (squirrel && redir->rd_fd < 3
             && squirrel[redir->rd_fd] < 0
            ) {
                squirrel[redir->rd_fd] = dup(redir->rd_fd);
            }
            if (openfd == REDIRFD_CLOSE) {
                /* "n>-" means "close me" */
                close(redir->rd_fd);
            } else {
                xdup2(openfd, redir->rd_fd);
                if (redir->rd_dup == REDIRFD_TO_FILE)
                    close(openfd);
            }
        }
    }
    return 0;
}

static void restore_redirects(int squirrel[])
{
    int i, fd;
    for (i = 0; i < 3; i++) {
        fd = squirrel[i];
        if (fd != -1) {
            /* We simply die on error */
            xmove_fd(fd, i);
        }
    }
}

static char *find_in_path(const char *arg)
{
    char *ret = NULL;
    const char *PATH = get_local_var_value("PATH");

    if (!PATH)
        return NULL;

    while (1) {
        const char *end = strchrnul(PATH, ':');
        int sz = end - PATH; /* must be int! */

        free(ret);
        if (sz != 0) {
            ret = xasprintf("%.*s/%s", sz, PATH, arg);
        } else {
            /* We have xxx::yyyy in $PATH,
             * it means "use current dir" */
            ret = xstrdup(arg);
        }
        if (access(ret, F_OK) == 0)
            break;

        if (*end == '\0') {
            free(ret);
            return NULL;
        }
        PATH = end + 1;
    }

    return ret;
}

static const struct built_in_command *find_builtin_helper(const char *name,
        const struct built_in_command *x,
        const struct built_in_command *end)
{
    while (x != end) {
        if (strcmp(name, x->b_cmd) != 0) {
            x++;
            continue;
        }
        debug_printf_exec("found builtin '%s'\n", name);
        return x;
    }
    return NULL;
}
static const struct built_in_command *find_builtin1(const char *name)
{
    return find_builtin_helper(name, bltins1, &bltins1[ARRAY_SIZE(bltins1)]);
}
static const struct built_in_command *find_builtin(const char *name)
{
    const struct built_in_command *x = find_builtin1(name);
    if (x)
        return x;
    return find_builtin_helper(name, bltins2, &bltins2[ARRAY_SIZE(bltins2)]);
}

#if ENABLE_HUSH_FUNCTIONS
static struct function **find_function_slot(const char *name)
{
    struct function **funcpp = &G.top_func;
    while (*funcpp) {
        if (strcmp(name, (*funcpp)->name) == 0) {
            break;
        }
        funcpp = &(*funcpp)->next;
    }
    return funcpp;
}

static const struct function *find_function(const char *name)
{
    const struct function *funcp = *find_function_slot(name);
    if (funcp)
        debug_printf_exec("found function '%s'\n", name);
    return funcp;
}

/* Note: takes ownership on name ptr */
static struct function *new_function(char *name)
{
    struct function **funcpp = find_function_slot(name);
    struct function *funcp = *funcpp;

    if (funcp != NULL) {
        struct command *cmd = funcp->parent_cmd;
        debug_printf_exec("func %p parent_cmd %p\n", funcp, cmd);
        if (!cmd) {
            debug_printf_exec("freeing & replacing function '%s'\n", funcp->name);
            free(funcp->name);
            /* Note: if !funcp->body, do not free body_as_string!
             * This is a special case of "-F name body" function:
             * body_as_string was not malloced! */
            if (funcp->body) {
                free_pipe_list(funcp->body);
# if !BB_MMU
                free(funcp->body_as_string);
# endif
            }
        } else {
            debug_printf_exec("reinserting in tree & replacing function '%s'\n", funcp->name);
            cmd->argv[0] = funcp->name;
            cmd->group = funcp->body;
# if !BB_MMU
            cmd->group_as_string = funcp->body_as_string;
# endif
        }
    } else {
        debug_printf_exec("remembering new function '%s'\n", name);
        funcp = *funcpp = xzalloc(sizeof(*funcp));
        /*funcp->next = NULL;*/
    }

    funcp->name = name;
    return funcp;
}

static void unset_func(const char *name)
{
    struct function **funcpp = find_function_slot(name);
    struct function *funcp = *funcpp;

    if (funcp != NULL) {
        debug_printf_exec("freeing function '%s'\n", funcp->name);
        *funcpp = funcp->next;
        /* funcp is unlinked now, deleting it.
         * Note: if !funcp->body, the function was created by
         * "-F name body", do not free ->body_as_string
         * and ->name as they were not malloced. */
        if (funcp->body) {
            free_pipe_list(funcp->body);
            free(funcp->name);
# if !BB_MMU
            free(funcp->body_as_string);
# endif
        }
        free(funcp);
    }
}

# if BB_MMU
#define exec_function(to_free, funcp, argv) \
    exec_function(funcp, argv)
# endif
static void exec_function(char ***to_free,
        const struct function *funcp,
        char **argv) NORETURN;
static void exec_function(char ***to_free,
        const struct function *funcp,
        char **argv)
{
# if BB_MMU
    int n = 1;

    argv[0] = G.global_argv[0];
    G.global_argv = argv;
    while (*++argv)
        n++;
    G.global_argc = n;
    /* On MMU, funcp->body is always non-NULL */
    n = run_list(funcp->body);
    fflush_all();
    _exit(n);
# else
    re_execute_shell(to_free,
            funcp->body_as_string,
            G.global_argv[0],
            argv + 1,
            NULL);
# endif
}

static int run_function(const struct function *funcp, char **argv)
{
    int rc;
    save_arg_t sv;
    smallint sv_flg;

    save_and_replace_G_args(&sv, argv);

    /* "we are in function, ok to use return" */
    sv_flg = G.flag_return_in_progress;
    G.flag_return_in_progress = -1;
# if ENABLE_HUSH_LOCAL
    G.func_nest_level++;
# endif

    /* On MMU, funcp->body is always non-NULL */
# if !BB_MMU
    if (!funcp->body) {
        /* Function defined by -F */
        parse_and_run_string(funcp->body_as_string);
        rc = G.last_exitcode;
    } else
# endif
    {
        rc = run_list(funcp->body);
    }

# if ENABLE_HUSH_LOCAL
    {
        struct variable *var;
        struct variable **var_pp;

        var_pp = &G.top_var;
        while ((var = *var_pp) != NULL) {
            if (var->func_nest_level < G.func_nest_level) {
                var_pp = &var->next;
                continue;
            }
            /* Unexport */
            if (var->flg_export)
                bb_unsetenv(var->varstr);
            /* Remove from global list */
            *var_pp = var->next;
            /* Free */
            if (!var->max_len)
                free(var->varstr);
            free(var);
        }
        G.func_nest_level--;
    }
# endif
    G.flag_return_in_progress = sv_flg;

    restore_G_args(&sv, argv);

    return rc;
}
#endif /* ENABLE_HUSH_FUNCTIONS */


#if BB_MMU
#define exec_builtin(to_free, x, argv) \
    exec_builtin(x, argv)
#else
#define exec_builtin(to_free, x, argv) \
    exec_builtin(to_free, argv)
#endif
static void exec_builtin(char ***to_free,
        const struct built_in_command *x,
        char **argv) NORETURN;
static void exec_builtin(char ***to_free,
        const struct built_in_command *x,
        char **argv)
{
#if BB_MMU
    int rcode;
    fflush_all();
    rcode = x->b_function(argv);
    fflush_all();
    _exit(rcode);
#else
    fflush_all();
    /* On NOMMU, we must never block!
     * Example: { sleep 99 | read line; } & echo Ok
     */
    re_execute_shell(to_free,
            argv[0],
            G.global_argv[0],
            G.global_argv + 1,
            argv);
#endif
}


static void execvp_or_die(char **argv) NORETURN;
static void execvp_or_die(char **argv)
{
    debug_printf_exec("execing '%s'\n", argv[0]);
    /* Don't propagate SIG_IGN to the child */
    if (SPECIAL_JOBSTOP_SIGS != 0)
        switch_off_special_sigs(G.special_sig_mask & SPECIAL_JOBSTOP_SIGS);
    execvp(argv[0], argv);
    bb_perror_msg("can't execute '%s'", argv[0]);
    _exit(127); /* bash compat */
}

#if ENABLE_HUSH_MODE_X
static void dump_cmd_in_x_mode(char **argv)
{
    if (G_x_mode && argv) {
        /* We want to output the line in one write op */
        char *buf, *p;
        int len;
        int n;

        len = 3;
        n = 0;
        while (argv[n])
            len += strlen(argv[n++]) + 1;
        buf = xmalloc(len);
        buf[0] = '+';
        p = buf + 1;
        n = 0;
        while (argv[n])
            p += sprintf(p, " %s", argv[n++]);
        *p++ = '\n';
        *p = '\0';
        fputs(buf, stderr);
        free(buf);
    }
}
#else
# define dump_cmd_in_x_mode(argv) ((void)0)
#endif

#if BB_MMU
#define pseudo_exec_argv(nommu_save, argv, assignment_cnt, argv_expanded) \
    pseudo_exec_argv(argv, assignment_cnt, argv_expanded)
#define pseudo_exec(nommu_save, command, argv_expanded) \
    pseudo_exec(command, argv_expanded)
#endif

/* Called after [v]fork() in run_pipe, or from builtin_exec.
 * Never returns.
 * Don't exit() here.  If you don't exec, use _exit instead.
 * The at_exit handlers apparently confuse the calling process,
 * in particular stdin handling. Not sure why? -- because of vfork! (vda)
 */
static void pseudo_exec_argv(nommu_save_t *nommu_save,
        char **argv, int assignment_cnt,
        char **argv_expanded) NORETURN;
static NOINLINE void pseudo_exec_argv(nommu_save_t *nommu_save,
        char **argv, int assignment_cnt,
        char **argv_expanded)
{
    char **new_env;

    new_env = expand_assignments(argv, assignment_cnt);
    dump_cmd_in_x_mode(new_env);

    if (!argv[assignment_cnt]) {
        /* Case when we are here: ... | var=val | ...
         * (note that we do not exit early, i.e., do not optimize out
         * expand_assignments(): think about ... | var=`sleep 1` | ...
         */
        free_strings(new_env);
        _exit(EXIT_SUCCESS);
    }

#if BB_MMU
    set_vars_and_save_old(new_env);
    free(new_env); /* optional */
    /* we can also destroy set_vars_and_save_old's return value,
     * to save memory */
#else
    nommu_save->new_env = new_env;
    nommu_save->old_vars = set_vars_and_save_old(new_env);
#endif

    if (argv_expanded) {
        argv = argv_expanded;
    } else {
        argv = expand_strvec_to_strvec(argv + assignment_cnt);
#if !BB_MMU
        nommu_save->argv = argv;
#endif
    }
    dump_cmd_in_x_mode(argv);

#if ENABLE_FEATURE_SH_STANDALONE || BB_MMU
    if (strchr(argv[0], '/') != NULL)
        goto skip;
#endif

    /* Check if the command matches any of the builtins.
     * Depending on context, this might be redundant.  But it's
     * easier to waste a few CPU cycles than it is to figure out
     * if this is one of those cases.
     */
    {
        /* On NOMMU, it is more expensive to re-execute shell
         * just in order to run echo or test builtin.
         * It's better to skip it here and run corresponding
         * non-builtin later. */
        const struct built_in_command *x;
        x = BB_MMU ? find_builtin(argv[0]) : find_builtin1(argv[0]);
        if (x) {
            exec_builtin(&nommu_save->argv_from_re_execing, x, argv);
        }
    }
#if ENABLE_HUSH_FUNCTIONS
    /* Check if the command matches any functions */
    {
        const struct function *funcp = find_function(argv[0]);
        if (funcp) {
            exec_function(&nommu_save->argv_from_re_execing, funcp, argv);
        }
    }
#endif

#if ENABLE_FEATURE_SH_STANDALONE
    /* Check if the command matches any busybox applets */
    {
        int a = find_applet_by_name(argv[0]);
        if (a >= 0) {
# if BB_MMU /* see above why on NOMMU it is not allowed */
            if (APPLET_IS_NOEXEC(a)) {
                debug_printf_exec("running applet '%s'\n", argv[0]);
                run_applet_no_and_exit(a, argv);
            }
# endif
            /* Re-exec ourselves */
            debug_printf_exec("re-execing applet '%s'\n", argv[0]);
            /* Don't propagate SIG_IGN to the child */
            if (SPECIAL_JOBSTOP_SIGS != 0)
                switch_off_special_sigs(G.special_sig_mask & SPECIAL_JOBSTOP_SIGS);
            execv(bb_busybox_exec_path, argv);
            /* If they called chroot or otherwise made the binary no longer
             * executable, fall through */
        }
    }
#endif

#if ENABLE_FEATURE_SH_STANDALONE || BB_MMU
 skip:
#endif
    execvp_or_die(argv);
}

/* Called after [v]fork() in run_pipe
 */
static void pseudo_exec(nommu_save_t *nommu_save,
        struct command *command,
        char **argv_expanded) NORETURN;
static void pseudo_exec(nommu_save_t *nommu_save,
        struct command *command,
        char **argv_expanded)
{
    if (command->argv) {
        pseudo_exec_argv(nommu_save, command->argv,
                command->assignment_cnt, argv_expanded);
    }

    if (command->group) {
        /* Cases when we are here:
         * ( list )
         * { list } &
         * ... | ( list ) | ...
         * ... | { list } | ...
         */
#if BB_MMU
        int rcode;
        debug_printf_exec("pseudo_exec: run_list\n");
        reset_traps_to_defaults();
        rcode = run_list(command->group);
        /* OK to leak memory by not calling free_pipe_list,
         * since this process is about to exit */
        _exit(rcode);
#else
        re_execute_shell(&nommu_save->argv_from_re_execing,
                command->group_as_string,
                G.global_argv[0],
                G.global_argv + 1,
                NULL);
#endif
    }

    /* Case when we are here: ... | >file */
    debug_printf_exec("pseudo_exec'ed null command\n");
    _exit(EXIT_SUCCESS);
}

#if ENABLE_HUSH_JOB
static const char *get_cmdtext(struct pipe *pi)
{
    char **argv;
    char *p;
    int len;

    /* This is subtle. ->cmdtext is created only on first backgrounding.
     * (Think "cat, <ctrl-z>, fg, <ctrl-z>, fg, <ctrl-z>...." here...)
     * On subsequent bg argv is trashed, but we won't use it */
    if (pi->cmdtext)
        return pi->cmdtext;
    argv = pi->cmds[0].argv;
    if (!argv || !argv[0]) {
        pi->cmdtext = xzalloc(1);
        return pi->cmdtext;
    }

    len = 0;
    do {
        len += strlen(*argv) + 1;
    } while (*++argv);
    p = xmalloc(len);
    pi->cmdtext = p;
    argv = pi->cmds[0].argv;
    do {
        len = strlen(*argv);
        memcpy(p, *argv, len);
        p += len;
        *p++ = ' ';
    } while (*++argv);
    p[-1] = '\0';
    return pi->cmdtext;
}

static void insert_bg_job(struct pipe *pi)
{
    struct pipe *job, **jobp;
    int i;

    /* Linear search for the ID of the job to use */
    pi->jobid = 1;
    for (job = G.job_list; job; job = job->next)
        if (job->jobid >= pi->jobid)
            pi->jobid = job->jobid + 1;

    /* Add job to the list of running jobs */
    jobp = &G.job_list;
    while ((job = *jobp) != NULL)
        jobp = &job->next;
    job = *jobp = xmalloc(sizeof(*job));

    *job = *pi; /* physical copy */
    job->next = NULL;
    job->cmds = xzalloc(sizeof(pi->cmds[0]) * pi->num_cmds);
    /* Cannot copy entire pi->cmds[] vector! This causes double frees */
    for (i = 0; i < pi->num_cmds; i++) {
        job->cmds[i].pid = pi->cmds[i].pid;
        /* all other fields are not used and stay zero */
    }
    job->cmdtext = xstrdup(get_cmdtext(pi));

    if (G_interactive_fd)
        printf("[%d] %d %s\n", job->jobid, job->cmds[0].pid, job->cmdtext);
    G.last_jobid = job->jobid;
}

static void remove_bg_job(struct pipe *pi)
{
    struct pipe *prev_pipe;

    if (pi == G.job_list) {
        G.job_list = pi->next;
    } else {
        prev_pipe = G.job_list;
        while (prev_pipe->next != pi)
            prev_pipe = prev_pipe->next;
        prev_pipe->next = pi->next;
    }
    if (G.job_list)
        G.last_jobid = G.job_list->jobid;
    else
        G.last_jobid = 0;
}

/* Remove a backgrounded job */
static void delete_finished_bg_job(struct pipe *pi)
{
    remove_bg_job(pi);
    free_pipe(pi);
}
#endif /* JOB */

/* Check to see if any processes have exited -- if they
 * have, figure out why and see if a job has completed */
static int checkjobs(struct pipe *fg_pipe)
{
    int attributes;
    int status;
#if ENABLE_HUSH_JOB
    struct pipe *pi;
#endif
    pid_t childpid;
    int rcode = 0;

    debug_printf_jobs("checkjobs %p\n", fg_pipe);

    attributes = WUNTRACED;
    if (fg_pipe == NULL)
        attributes |= WNOHANG;

    errno = 0;
#if ENABLE_HUSH_FAST
    if (G.handled_SIGCHLD == G.count_SIGCHLD) {
//bb_error_msg("[%d] checkjobs: G.count_SIGCHLD:%d G.handled_SIGCHLD:%d children?:%d fg_pipe:%p",
//getpid(), G.count_SIGCHLD, G.handled_SIGCHLD, G.we_have_children, fg_pipe);
        /* There was neither fork nor SIGCHLD since last waitpid */
        /* Avoid doing waitpid syscall if possible */
        if (!G.we_have_children) {
            errno = ECHILD;
            return -1;
        }
        if (fg_pipe == NULL) { /* is WNOHANG set? */
            /* We have children, but they did not exit
             * or stop yet (we saw no SIGCHLD) */
            return 0;
        }
        /* else: !WNOHANG, waitpid will block, can't short-circuit */
    }
#endif

/* Do we do this right?
 * bash-3.00# sleep 20 | false
 * <ctrl-Z pressed>
 * [3]+  Stopped          sleep 20 | false
 * bash-3.00# echo $?
 * 1   <========== bg pipe is not fully done, but exitcode is already known!
 * [hush 1.14.0: yes we do it right]
 */
 wait_more:
    while (1) {
        int i;
        int dead;

#if ENABLE_HUSH_FAST
        i = G.count_SIGCHLD;
#endif
        childpid = waitpid(-1, &status, attributes);
        if (childpid <= 0) {
            if (childpid && errno != ECHILD)
                bb_perror_msg("waitpid");
#if ENABLE_HUSH_FAST
            else { /* Until next SIGCHLD, waitpid's are useless */
                G.we_have_children = (childpid == 0);
                G.handled_SIGCHLD = i;
//bb_error_msg("[%d] checkjobs: waitpid returned <= 0, G.count_SIGCHLD:%d G.handled_SIGCHLD:%d", getpid(), G.count_SIGCHLD, G.handled_SIGCHLD);
            }
#endif
            break;
        }
        dead = WIFEXITED(status) || WIFSIGNALED(status);

#if DEBUG_JOBS
        if (WIFSTOPPED(status))
            debug_printf_jobs("pid %d stopped by sig %d (exitcode %d)\n",
                    childpid, WSTOPSIG(status), WEXITSTATUS(status));
        if (WIFSIGNALED(status))
            debug_printf_jobs("pid %d killed by sig %d (exitcode %d)\n",
                    childpid, WTERMSIG(status), WEXITSTATUS(status));
        if (WIFEXITED(status))
            debug_printf_jobs("pid %d exited, exitcode %d\n",
                    childpid, WEXITSTATUS(status));
#endif
        /* Were we asked to wait for fg pipe? */
        if (fg_pipe) {
            i = fg_pipe->num_cmds;
            while (--i >= 0) {
                debug_printf_jobs("check pid %d\n", fg_pipe->cmds[i].pid);
                if (fg_pipe->cmds[i].pid != childpid)
                    continue;
                if (dead) {
                    int ex;
                    fg_pipe->cmds[i].pid = 0;
                    fg_pipe->alive_cmds--;
                    ex = WEXITSTATUS(status);
                    /* bash prints killer signal's name for *last*
                     * process in pipe (prints just newline for SIGINT/SIGPIPE).
                     * Mimic this. Example: "sleep 5" + (^\ or kill -QUIT)
                     */
                    if (WIFSIGNALED(status)) {
                        int sig = WTERMSIG(status);
                        if (i == fg_pipe->num_cmds-1)
                            /* TODO: use strsignal() instead for bash compat? but that's bloat... */
                            puts(sig == SIGINT || sig == SIGPIPE ? "" : get_signame(sig));
                        /* TODO: if (WCOREDUMP(status)) + " (core dumped)"; */
                        /* TODO: MIPS has 128 sigs (1..128), what if sig==128 here?
                         * Maybe we need to use sig | 128? */
                        ex = sig + 128;
                    }
                    fg_pipe->cmds[i].cmd_exitcode = ex;
                } else {
                    fg_pipe->stopped_cmds++;
                }
                debug_printf_jobs("fg_pipe: alive_cmds %d stopped_cmds %d\n",
                        fg_pipe->alive_cmds, fg_pipe->stopped_cmds);
                if (fg_pipe->alive_cmds == fg_pipe->stopped_cmds) {
                    /* All processes in fg pipe have exited or stopped */
                    i = fg_pipe->num_cmds;
                    while (--i >= 0) {
                        rcode = fg_pipe->cmds[i].cmd_exitcode;
                        /* usually last process gives overall exitstatus,
                         * but with "set -o pipefail", last *failed* process does */
                        if (G.o_opt[OPT_O_PIPEFAIL] == 0 || rcode != 0)
                            break;
                    }
                    IF_HAS_KEYWORDS(if (fg_pipe->pi_inverted) rcode = !rcode;)
/* Note: *non-interactive* bash does not continue if all processes in fg pipe
 * are stopped. Testcase: "cat | cat" in a script (not on command line!)
 * and "killall -STOP cat" */
                    if (G_interactive_fd) {
#if ENABLE_HUSH_JOB
                        if (fg_pipe->alive_cmds != 0)
                            insert_bg_job(fg_pipe);
#endif
                        return rcode;
                    }
                    if (fg_pipe->alive_cmds == 0)
                        return rcode;
                }
                /* There are still running processes in the fg pipe */
                goto wait_more; /* do waitpid again */
            }
            /* it wasnt fg_pipe, look for process in bg pipes */
        }

#if ENABLE_HUSH_JOB
        /* We asked to wait for bg or orphaned children */
        /* No need to remember exitcode in this case */
        for (pi = G.job_list; pi; pi = pi->next) {
            for (i = 0; i < pi->num_cmds; i++) {
                if (pi->cmds[i].pid == childpid)
                    goto found_pi_and_prognum;
            }
        }
        /* Happens when shell is used as init process (init=/bin/sh) */
        debug_printf("checkjobs: pid %d was not in our list!\n", childpid);
        continue; /* do waitpid again */

 found_pi_and_prognum:
        if (dead) {
            /* child exited */
            pi->cmds[i].pid = 0;
            pi->alive_cmds--;
            if (!pi->alive_cmds) {
                if (G_interactive_fd)
                    printf(JOB_STATUS_FORMAT, pi->jobid,
                            "Done", pi->cmdtext);
                delete_finished_bg_job(pi);
            }
        } else {
            /* child stopped */
            pi->stopped_cmds++;
        }
#endif
    } /* while (waitpid succeeds)... */

    return rcode;
}

#if ENABLE_HUSH_JOB
static int checkjobs_and_fg_shell(struct pipe *fg_pipe)
{
    pid_t p;
    int rcode = checkjobs(fg_pipe);
    if (G_saved_tty_pgrp) {
        /* Job finished, move the shell to the foreground */
        p = getpgrp(); /* our process group id */
        debug_printf_jobs("fg'ing ourself: getpgrp()=%d\n", (int)p);
        tcsetpgrp(G_interactive_fd, p);
    }
    return rcode;
}
#endif

/* Start all the jobs, but don't wait for anything to finish.
 * See checkjobs().
 *
 * Return code is normally -1, when the caller has to wait for children
 * to finish to determine the exit status of the pipe.  If the pipe
 * is a simple builtin command, however, the action is done by the
 * time run_pipe returns, and the exit code is provided as the
 * return value.
 *
 * Returns -1 only if started some children. IOW: we have to
 * mask out retvals of builtins etc with 0xff!
 *
 * The only case when we do not need to [v]fork is when the pipe
 * is single, non-backgrounded, non-subshell command. Examples:
 * cmd ; ...   { list } ; ...
 * cmd && ...  { list } && ...
 * cmd || ...  { list } || ...
 * If it is, then we can run cmd as a builtin, NOFORK,
 * or (if SH_STANDALONE) an applet, and we can run the { list }
 * with run_list. If it isn't one of these, we fork and exec cmd.
 *
 * Cases when we must fork:
 * non-single:   cmd | cmd
 * backgrounded: cmd &     { list } &
 * subshell:     ( list ) [&]
 */
#if !ENABLE_HUSH_MODE_X
#define redirect_and_varexp_helper(new_env_p, old_vars_p, command, squirrel, argv_expanded) \
    redirect_and_varexp_helper(new_env_p, old_vars_p, command, squirrel)
#endif
static int redirect_and_varexp_helper(char ***new_env_p,
        struct variable **old_vars_p,
        struct command *command,
        int squirrel[3],
        char **argv_expanded)
{
    /* setup_redirects acts on file descriptors, not FILEs.
     * This is perfect for work that comes after exec().
     * Is it really safe for inline use?  Experimentally,
     * things seem to work. */
    int rcode = setup_redirects(command, squirrel);
    if (rcode == 0) {
        char **new_env = expand_assignments(command->argv, command->assignment_cnt);
        *new_env_p = new_env;
        dump_cmd_in_x_mode(new_env);
        dump_cmd_in_x_mode(argv_expanded);
        if (old_vars_p)
            *old_vars_p = set_vars_and_save_old(new_env);
    }
    return rcode;
}
static NOINLINE int run_pipe(struct pipe *pi)
{
    static const char *const null_ptr = NULL;

    int cmd_no;
    int next_infd;
    struct command *command;
    char **argv_expanded;
    char **argv;
    /* it is not always needed, but we aim to smaller code */
    int squirrel[] = { -1, -1, -1 };
    int rcode;

    debug_printf_exec("run_pipe start: members:%d\n", pi->num_cmds);
    debug_enter();

    /* Testcase: set -- q w e; (IFS='' echo "$*"; IFS=''; echo "$*"); echo "$*"
     * Result should be 3 lines: q w e, qwe, q w e
     */
    G.ifs = get_local_var_value("IFS");
    if (!G.ifs)
        G.ifs = defifs;

    IF_HUSH_JOB(pi->pgrp = -1;)
    pi->stopped_cmds = 0;
    command = &pi->cmds[0];
    argv_expanded = NULL;

    if (pi->num_cmds != 1
     || pi->followup == PIPE_BG
     || command->cmd_type == CMD_SUBSHELL
    ) {
        goto must_fork;
    }

    pi->alive_cmds = 1;

    debug_printf_exec(": group:%p argv:'%s'\n",
        command->group, command->argv ? command->argv[0] : "NONE");

    if (command->group) {
#if ENABLE_HUSH_FUNCTIONS
        if (command->cmd_type == CMD_FUNCDEF) {
            /* "executing" func () { list } */
            struct function *funcp;

            funcp = new_function(command->argv[0]);
            /* funcp->name is already set to argv[0] */
            funcp->body = command->group;
# if !BB_MMU
            funcp->body_as_string = command->group_as_string;
            command->group_as_string = NULL;
# endif
            command->group = NULL;
            command->argv[0] = NULL;
            debug_printf_exec("cmd %p has child func at %p\n", command, funcp);
            funcp->parent_cmd = command;
            command->child_func = funcp;

            debug_printf_exec("run_pipe: return EXIT_SUCCESS\n");
            debug_leave();
            return EXIT_SUCCESS;
        }
#endif
        /* { list } */
        debug_printf("non-subshell group\n");
        rcode = 1; /* exitcode if redir failed */
        if (setup_redirects(command, squirrel) == 0) {
            debug_printf_exec(": run_list\n");
            rcode = run_list(command->group) & 0xff;
        }
        restore_redirects(squirrel);
        IF_HAS_KEYWORDS(if (pi->pi_inverted) rcode = !rcode;)
        debug_leave();
        debug_printf_exec("run_pipe: return %d\n", rcode);
        return rcode;
    }

    argv = command->argv ? command->argv : (char **) &null_ptr;
    {
        const struct built_in_command *x;
#if ENABLE_HUSH_FUNCTIONS
        const struct function *funcp;
#else
        enum { funcp = 0 };
#endif
        char **new_env = NULL;
        struct variable *old_vars = NULL;

        if (argv[command->assignment_cnt] == NULL) {
            /* Assignments, but no command */
            /* Ensure redirects take effect (that is, create files).
             * Try "a=t >file" */
#if 0 /* A few cases in testsuite fail with this code. FIXME */
            rcode = redirect_and_varexp_helper(&new_env, /*old_vars:*/ NULL, command, squirrel, /*argv_expanded:*/ NULL);
            /* Set shell variables */
            if (new_env) {
                argv = new_env;
                while (*argv) {
                    set_local_var(*argv, /*exp:*/ 0, /*lvl:*/ 0, /*ro:*/ 0);
                    /* Do we need to flag set_local_var() errors?
                     * "assignment to readonly var" and "putenv error"
                     */
                    argv++;
                }
            }
            /* Redirect error sets $? to 1. Otherwise,
             * if evaluating assignment value set $?, retain it.
             * Try "false; q=`exit 2`; echo $?" - should print 2: */
            if (rcode == 0)
                rcode = G.last_exitcode;
            /* Exit, _skipping_ variable restoring code: */
            goto clean_up_and_ret0;

#else /* Older, bigger, but more correct code */

            rcode = setup_redirects(command, squirrel);
            restore_redirects(squirrel);
            /* Set shell variables */
            if (G_x_mode)
                bb_putchar_stderr('+');
            while (*argv) {
                char *p = expand_string_to_string(*argv, /*unbackslash:*/ 1);
                if (G_x_mode)
                    fprintf(stderr, " %s", p);
                debug_printf_exec("set shell var:'%s'->'%s'\n",
                        *argv, p);
                set_local_var(p, /*exp:*/ 0, /*lvl:*/ 0, /*ro:*/ 0);
                /* Do we need to flag set_local_var() errors?
                 * "assignment to readonly var" and "putenv error"
                 */
                argv++;
            }
            if (G_x_mode)
                bb_putchar_stderr('\n');
            /* Redirect error sets $? to 1. Otherwise,
             * if evaluating assignment value set $?, retain it.
             * Try "false; q=`exit 2`; echo $?" - should print 2: */
            if (rcode == 0)
                rcode = G.last_exitcode;
            IF_HAS_KEYWORDS(if (pi->pi_inverted) rcode = !rcode;)
            debug_leave();
            debug_printf_exec("run_pipe: return %d\n", rcode);
            return rcode;
#endif
        }

        /* Expand the rest into (possibly) many strings each */
#if ENABLE_HUSH_BASH_COMPAT
        if (command->cmd_type == CMD_SINGLEWORD_NOGLOB) {
            argv_expanded = expand_strvec_to_strvec_singleword_noglob(argv + command->assignment_cnt);
        } else
#endif
        {
            argv_expanded = expand_strvec_to_strvec(argv + command->assignment_cnt);
        }

        /* if someone gives us an empty string: `cmd with empty output` */
        if (!argv_expanded[0]) {
            free(argv_expanded);
            debug_leave();
            return G.last_exitcode;
        }

        x = find_builtin(argv_expanded[0]);
#if ENABLE_HUSH_FUNCTIONS
        funcp = NULL;
        if (!x)
            funcp = find_function(argv_expanded[0]);
#endif
        if (x || funcp) {
            if (!funcp) {
                if (x->b_function == builtin_exec && argv_expanded[1] == NULL) {
                    debug_printf("exec with redirects only\n");
                    rcode = setup_redirects(command, NULL);
                    goto clean_up_and_ret1;
                }
            }
            rcode = redirect_and_varexp_helper(&new_env, &old_vars, command, squirrel, argv_expanded);
            if (rcode == 0) {
                if (!funcp) {
                    debug_printf_exec(": builtin '%s' '%s'...\n",
                        x->b_cmd, argv_expanded[1]);
                    fflush_all();
                    rcode = x->b_function(argv_expanded) & 0xff;
                    fflush_all();
                }
#if ENABLE_HUSH_FUNCTIONS
                else {
# if ENABLE_HUSH_LOCAL
                    struct variable **sv;
                    sv = G.shadowed_vars_pp;
                    G.shadowed_vars_pp = &old_vars;
# endif
                    debug_printf_exec(": function '%s' '%s'...\n",
                        funcp->name, argv_expanded[1]);
                    rcode = run_function(funcp, argv_expanded) & 0xff;
# if ENABLE_HUSH_LOCAL
                    G.shadowed_vars_pp = sv;
# endif
                }
#endif
            }
 clean_up_and_ret:
            unset_vars(new_env);
            add_vars(old_vars);
/* clean_up_and_ret0: */
            restore_redirects(squirrel);
 clean_up_and_ret1:
            free(argv_expanded);
            IF_HAS_KEYWORDS(if (pi->pi_inverted) rcode = !rcode;)
            debug_leave();
            debug_printf_exec("run_pipe return %d\n", rcode);
            return rcode;
        }

        if (ENABLE_FEATURE_SH_NOFORK) {
            int n = find_applet_by_name(argv_expanded[0]);
            if (n >= 0 && APPLET_IS_NOFORK(n)) {
                rcode = redirect_and_varexp_helper(&new_env, &old_vars, command, squirrel, argv_expanded);
                if (rcode == 0) {
                    debug_printf_exec(": run_nofork_applet '%s' '%s'...\n",
                        argv_expanded[0], argv_expanded[1]);
                    rcode = run_nofork_applet(n, argv_expanded);
                }
                goto clean_up_and_ret;
            }
        }
        /* It is neither builtin nor applet. We must fork. */
    }

 must_fork:
    /* NB: argv_expanded may already be created, and that
     * might include `cmd` runs! Do not rerun it! We *must*
     * use argv_expanded if it's non-NULL */

    /* Going to fork a child per each pipe member */
    pi->alive_cmds = 0;
    next_infd = 0;

    cmd_no = 0;
    while (cmd_no < pi->num_cmds) {
        struct fd_pair pipefds;
#if !BB_MMU
        volatile nommu_save_t nommu_save;
        nommu_save.new_env = NULL;
        nommu_save.old_vars = NULL;
        nommu_save.argv = NULL;
        nommu_save.argv_from_re_execing = NULL;
#endif
        command = &pi->cmds[cmd_no];
        cmd_no++;
        if (command->argv) {
            debug_printf_exec(": pipe member '%s' '%s'...\n",
                    command->argv[0], command->argv[1]);
        } else {
            debug_printf_exec(": pipe member with no argv\n");
        }

        /* pipes are inserted between pairs of commands */
        pipefds.rd = 0;
        pipefds.wr = 1;
        if (cmd_no < pi->num_cmds)
            xpiped_pair(pipefds);

        command->pid = BB_MMU ? fork() : vfork();
        if (!command->pid) { /* child */
#if ENABLE_HUSH_JOB
            disable_restore_tty_pgrp_on_exit();
            CLEAR_RANDOM_T(&G.random_gen); /* or else $RANDOM repeats in child */

            /* Every child adds itself to new process group
             * with pgid == pid_of_first_child_in_pipe */
            if (G.run_list_level == 1 && G_interactive_fd) {
                pid_t pgrp;
                pgrp = pi->pgrp;
                if (pgrp < 0) /* true for 1st process only */
                    pgrp = getpid();
                if (setpgid(0, pgrp) == 0
                 && pi->followup != PIPE_BG
                 && G_saved_tty_pgrp /* we have ctty */
                ) {
                    /* We do it in *every* child, not just first,
                     * to avoid races */
                    tcsetpgrp(G_interactive_fd, pgrp);
                }
            }
#endif
            if (pi->alive_cmds == 0 && pi->followup == PIPE_BG) {
                /* 1st cmd in backgrounded pipe
                 * should have its stdin /dev/null'ed */
                close(0);
                if (open(bb_dev_null, O_RDONLY))
                    xopen("/", O_RDONLY);
            } else {
                xmove_fd(next_infd, 0);
            }
            xmove_fd(pipefds.wr, 1);
            if (pipefds.rd > 1)
                close(pipefds.rd);
            /* Like bash, explicit redirects override pipes,
             * and the pipe fd is available for dup'ing. */
            if (setup_redirects(command, NULL))
                _exit(1);

            /* Stores to nommu_save list of env vars putenv'ed
             * (NOMMU, on MMU we don't need that) */
            /* cast away volatility... */
            pseudo_exec((nommu_save_t*) &nommu_save, command, argv_expanded);
            /* pseudo_exec() does not return */
        }

        /* parent or error */
#if ENABLE_HUSH_FAST
        G.count_SIGCHLD++;
//bb_error_msg("[%d] fork in run_pipe: G.count_SIGCHLD:%d G.handled_SIGCHLD:%d", getpid(), G.count_SIGCHLD, G.handled_SIGCHLD);
#endif
        enable_restore_tty_pgrp_on_exit();
#if !BB_MMU
        /* Clean up after vforked child */
        free(nommu_save.argv);
        free(nommu_save.argv_from_re_execing);
        unset_vars(nommu_save.new_env);
        add_vars(nommu_save.old_vars);
#endif
        free(argv_expanded);
        argv_expanded = NULL;
        if (command->pid < 0) { /* [v]fork failed */
            /* Clearly indicate, was it fork or vfork */
            bb_perror_msg(BB_MMU ? "vfork"+1 : "vfork");
        } else {
            pi->alive_cmds++;
#if ENABLE_HUSH_JOB
            /* Second and next children need to know pid of first one */
            if (pi->pgrp < 0)
                pi->pgrp = command->pid;
#endif
        }

        if (cmd_no > 1)
            close(next_infd);
        if (cmd_no < pi->num_cmds)
            close(pipefds.wr);
        /* Pass read (output) pipe end to next iteration */
        next_infd = pipefds.rd;
    }

    if (!pi->alive_cmds) {
        debug_leave();
        debug_printf_exec("run_pipe return 1 (all forks failed, no children)\n");
        return 1;
    }

    debug_leave();
    debug_printf_exec("run_pipe return -1 (%u children started)\n", pi->alive_cmds);
    return -1;
}

/* NB: called by pseudo_exec, and therefore must not modify any
 * global data until exec/_exit (we can be a child after vfork!) */
static int run_list(struct pipe *pi)
{
#if ENABLE_HUSH_CASE
    char *case_word = NULL;
#endif
#if ENABLE_HUSH_LOOPS
    struct pipe *loop_top = NULL;
    char **for_lcur = NULL;
    char **for_list = NULL;
#endif
    smallint last_followup;
    smalluint rcode;
#if ENABLE_HUSH_IF || ENABLE_HUSH_CASE
    smalluint cond_code = 0;
#else
    enum { cond_code = 0 };
#endif
#if HAS_KEYWORDS
    smallint rword;      /* RES_foo */
    smallint last_rword; /* ditto */
#endif

    debug_printf_exec("run_list start lvl %d\n", G.run_list_level);
    debug_enter();

#if ENABLE_HUSH_LOOPS
    /* Check syntax for "for" */
    {
        struct pipe *cpipe;
        for (cpipe = pi; cpipe; cpipe = cpipe->next) {
            if (cpipe->res_word != RES_FOR && cpipe->res_word != RES_IN)
                continue;
            /* current word is FOR or IN (BOLD in comments below) */
            if (cpipe->next == NULL) {
                syntax_error("malformed for");
                debug_leave();
                debug_printf_exec("run_list lvl %d return 1\n", G.run_list_level);
                return 1;
            }
            /* "FOR v; do ..." and "for v IN a b; do..." are ok */
            if (cpipe->next->res_word == RES_DO)
                continue;
            /* next word is not "do". It must be "in" then ("FOR v in ...") */
            if (cpipe->res_word == RES_IN /* "for v IN a b; not_do..."? */
             || cpipe->next->res_word != RES_IN /* FOR v not_do_and_not_in..."? */
            ) {
                syntax_error("malformed for");
                debug_leave();
                debug_printf_exec("run_list lvl %d return 1\n", G.run_list_level);
                return 1;
            }
        }
    }
#endif

    /* Past this point, all code paths should jump to ret: label
     * in order to return, no direct "return" statements please.
     * This helps to ensure that no memory is leaked. */

#if ENABLE_HUSH_JOB
    G.run_list_level++;
#endif

#if HAS_KEYWORDS
    rword = RES_NONE;
    last_rword = RES_XXXX;
#endif
    last_followup = PIPE_SEQ;
    rcode = G.last_exitcode;

    /* Go through list of pipes, (maybe) executing them. */
    for (; pi; pi = IF_HUSH_LOOPS(rword == RES_DONE ? loop_top : ) pi->next) {
        if (G.flag_SIGINT)
            break;

        IF_HAS_KEYWORDS(rword = pi->res_word;)
        debug_printf_exec(": rword=%d cond_code=%d last_rword=%d\n",
                rword, cond_code, last_rword);
#if ENABLE_HUSH_LOOPS
        if ((rword == RES_WHILE || rword == RES_UNTIL || rword == RES_FOR)
         && loop_top == NULL /* avoid bumping G.depth_of_loop twice */
        ) {
            /* start of a loop: remember where loop starts */
            loop_top = pi;
            G.depth_of_loop++;
        }
#endif
        /* Still in the same "if...", "then..." or "do..." branch? */
        if (IF_HAS_KEYWORDS(rword == last_rword &&) 1) {
            if ((rcode == 0 && last_followup == PIPE_OR)
             || (rcode != 0 && last_followup == PIPE_AND)
            ) {
                /* It is "<true> || CMD" or "<false> && CMD"
                 * and we should not execute CMD */
                debug_printf_exec("skipped cmd because of || or &&\n");
                last_followup = pi->followup;
                goto dont_check_jobs_but_continue;
            }
        }
        last_followup = pi->followup;
        IF_HAS_KEYWORDS(last_rword = rword;)
#if ENABLE_HUSH_IF
        if (cond_code) {
            if (rword == RES_THEN) {
                /* if false; then ... fi has exitcode 0! */
                G.last_exitcode = rcode = EXIT_SUCCESS;
                /* "if <false> THEN cmd": skip cmd */
                continue;
            }
        } else {
            if (rword == RES_ELSE || rword == RES_ELIF) {
                /* "if <true> then ... ELSE/ELIF cmd":
                 * skip cmd and all following ones */
                break;
            }
        }
#endif
#if ENABLE_HUSH_LOOPS
        if (rword == RES_FOR) { /* && pi->num_cmds - always == 1 */
            if (!for_lcur) {
                /* first loop through for */

                static const char encoded_dollar_at[] ALIGN1 = {
                    SPECIAL_VAR_SYMBOL, '@' | 0x80, SPECIAL_VAR_SYMBOL, '\0'
                }; /* encoded representation of "$@" */
                static const char *const encoded_dollar_at_argv[] = {
                    encoded_dollar_at, NULL
                }; /* argv list with one element: "$@" */
                char **vals;

                vals = (char**)encoded_dollar_at_argv;
                if (pi->next->res_word == RES_IN) {
                    /* if no variable values after "in" we skip "for" */
                    if (!pi->next->cmds[0].argv) {
                        G.last_exitcode = rcode = EXIT_SUCCESS;
                        debug_printf_exec(": null FOR: exitcode EXIT_SUCCESS\n");
                        break;
                    }
                    vals = pi->next->cmds[0].argv;
                } /* else: "for var; do..." -> assume "$@" list */
                /* create list of variable values */
                debug_print_strings("for_list made from", vals);
                for_list = expand_strvec_to_strvec(vals);
                for_lcur = for_list;
                debug_print_strings("for_list", for_list);
            }
            if (!*for_lcur) {
                /* "for" loop is over, clean up */
                free(for_list);
                for_list = NULL;
                for_lcur = NULL;
                break;
            }
            /* Insert next value from for_lcur */
            /* note: *for_lcur already has quotes removed, $var expanded, etc */
            set_local_var(xasprintf("%s=%s", pi->cmds[0].argv[0], *for_lcur++), /*exp:*/ 0, /*lvl:*/ 0, /*ro:*/ 0);
            continue;
        }
        if (rword == RES_IN) {
            continue; /* "for v IN list;..." - "in" has no cmds anyway */
        }
        if (rword == RES_DONE) {
            continue; /* "done" has no cmds too */
        }
#endif
#if ENABLE_HUSH_CASE
        if (rword == RES_CASE) {
            case_word = expand_strvec_to_string(pi->cmds->argv);
            continue;
        }
        if (rword == RES_MATCH) {
            char **argv;

            if (!case_word) /* "case ... matched_word) ... WORD)": we executed selected branch, stop */
                break;
            /* all prev words didn't match, does this one match? */
            argv = pi->cmds->argv;
            while (*argv) {
                char *pattern = expand_string_to_string(*argv, /*unbackslash:*/ 1);
                /* TODO: which FNM_xxx flags to use? */
                cond_code = (fnmatch(pattern, case_word, /*flags:*/ 0) != 0);
                free(pattern);
                if (cond_code == 0) { /* match! we will execute this branch */
                    free(case_word); /* make future "word)" stop */
                    case_word = NULL;
                    break;
                }
                argv++;
            }
            continue;
        }
        if (rword == RES_CASE_BODY) { /* inside of a case branch */
            if (cond_code != 0)
                continue; /* not matched yet, skip this pipe */
        }
#endif
        /* Just pressing <enter> in shell should check for jobs.
         * OTOH, in non-interactive shell this is useless
         * and only leads to extra job checks */
        if (pi->num_cmds == 0) {
            if (G_interactive_fd)
                goto check_jobs_and_continue;
            continue;
        }

        /* After analyzing all keywords and conditions, we decided
         * to execute this pipe. NB: have to do checkjobs(NULL)
         * after run_pipe to collect any background children,
         * even if list execution is to be stopped. */
        debug_printf_exec(": run_pipe with %d members\n", pi->num_cmds);
        {
            int r;
#if ENABLE_HUSH_LOOPS
            G.flag_break_continue = 0;
#endif
            rcode = r = run_pipe(pi); /* NB: rcode is a smallint */
            if (r != -1) {
                /* We ran a builtin, function, or group.
                 * rcode is already known
                 * and we don't need to wait for anything. */
                G.last_exitcode = rcode;
                debug_printf_exec(": builtin/func exitcode %d\n", rcode);
                check_and_run_traps();
#if ENABLE_HUSH_LOOPS
                /* Was it "break" or "continue"? */
                if (G.flag_break_continue) {
                    smallint fbc = G.flag_break_continue;
                    /* We might fall into outer *loop*,
                     * don't want to break it too */
                    if (loop_top) {
                        G.depth_break_continue--;
                        if (G.depth_break_continue == 0)
                            G.flag_break_continue = 0;
                        /* else: e.g. "continue 2" should *break* once, *then* continue */
                    } /* else: "while... do... { we are here (innermost list is not a loop!) };...done" */
                    if (G.depth_break_continue != 0 || fbc == BC_BREAK) {
                        checkjobs(NULL);
                        break;
                    }
                    /* "continue": simulate end of loop */
                    rword = RES_DONE;
                    continue;
                }
#endif
#if ENABLE_HUSH_FUNCTIONS
                if (G.flag_return_in_progress == 1) {
                    checkjobs(NULL);
                    break;
                }
#endif
            } else if (pi->followup == PIPE_BG) {
                /* What does bash do with attempts to background builtins? */
                /* even bash 3.2 doesn't do that well with nested bg:
                 * try "{ { sleep 10; echo DEEP; } & echo HERE; } &".
                 * I'm NOT treating inner &'s as jobs */
                check_and_run_traps();
#if ENABLE_HUSH_JOB
                if (G.run_list_level == 1)
                    insert_bg_job(pi);
#endif
                /* Last command's pid goes to $! */
                G.last_bg_pid = pi->cmds[pi->num_cmds - 1].pid;
                G.last_exitcode = rcode = EXIT_SUCCESS;
                debug_printf_exec(": cmd&: exitcode EXIT_SUCCESS\n");
            } else {
#if ENABLE_HUSH_JOB
                if (G.run_list_level == 1 && G_interactive_fd) {
                    /* Waits for completion, then fg's main shell */
                    rcode = checkjobs_and_fg_shell(pi);
                    debug_printf_exec(": checkjobs_and_fg_shell exitcode %d\n", rcode);
                    check_and_run_traps();
                } else
#endif
                { /* This one just waits for completion */
                    rcode = checkjobs(pi);
                    debug_printf_exec(": checkjobs exitcode %d\n", rcode);
                    check_and_run_traps();
                }
                G.last_exitcode = rcode;
            }
        }

        /* Analyze how result affects subsequent commands */
#if ENABLE_HUSH_IF
        if (rword == RES_IF || rword == RES_ELIF)
            cond_code = rcode;
#endif
 check_jobs_and_continue:
        checkjobs(NULL);
 dont_check_jobs_but_continue: ;
#if ENABLE_HUSH_LOOPS
        /* Beware of "while false; true; do ..."! */
        if (pi->next
         && (pi->next->res_word == RES_DO || pi->next->res_word == RES_DONE)
         /* check for RES_DONE is needed for "while ...; do \n done" case */
        ) {
            if (rword == RES_WHILE) {
                if (rcode) {
                    /* "while false; do...done" - exitcode 0 */
                    G.last_exitcode = rcode = EXIT_SUCCESS;
                    debug_printf_exec(": while expr is false: breaking (exitcode:EXIT_SUCCESS)\n");
                    break;
                }
            }
            if (rword == RES_UNTIL) {
                if (!rcode) {
                    debug_printf_exec(": until expr is true: breaking\n");
                    break;
                }
            }
        }
#endif
    } /* for (pi) */

#if ENABLE_HUSH_JOB
    G.run_list_level--;
#endif
#if ENABLE_HUSH_LOOPS
    if (loop_top)
        G.depth_of_loop--;
    free(for_list);
#endif
#if ENABLE_HUSH_CASE
    free(case_word);
#endif
    debug_leave();
    debug_printf_exec("run_list lvl %d return %d\n", G.run_list_level + 1, rcode);
    return rcode;
}

/* Select which version we will use */
static int run_and_free_list(struct pipe *pi)
{
    int rcode = 0;
    debug_printf_exec("run_and_free_list entered\n");
    if (!G.o_opt[OPT_O_NOEXEC]) {
        debug_printf_exec(": run_list: 1st pipe with %d cmds\n", pi->num_cmds);
        rcode = run_list(pi);
    }
    /* free_pipe_list has the side effect of clearing memory.
     * In the long run that function can be merged with run_list,
     * but doing that now would hobble the debugging effort. */
    free_pipe_list(pi);
    debug_printf_exec("run_and_free_list return %d\n", rcode);
    return rcode;
}


static void install_sighandlers(unsigned mask)
{
    sighandler_t old_handler;
    unsigned sig = 0;
    while ((mask >>= 1) != 0) {
        sig++;
        if (!(mask & 1))
            continue;
        old_handler = install_sighandler(sig, pick_sighandler(sig));
        /* POSIX allows shell to re-enable SIGCHLD
         * even if it was SIG_IGN on entry.
         * Therefore we skip IGN check for it:
         */
        if (sig == SIGCHLD)
            continue;
        if (old_handler == SIG_IGN) {
            /* oops... restore back to IGN, and record this fact */
            install_sighandler(sig, old_handler);
            if (!G.traps)
                G.traps = xzalloc(sizeof(G.traps[0]) * NSIG);
            free(G.traps[sig]);
            G.traps[sig] = xzalloc(1); /* == xstrdup(""); */
        }
    }
}

/* Called a few times only (or even once if "sh -c") */
static void install_special_sighandlers(void)
{
    unsigned mask;

    /* Which signals are shell-special? */
    mask = (1 << SIGQUIT) | (1 << SIGCHLD);
    if (G_interactive_fd) {
        mask |= SPECIAL_INTERACTIVE_SIGS;
        if (G_saved_tty_pgrp) /* we have ctty, job control sigs work */
            mask |= SPECIAL_JOBSTOP_SIGS;
    }
    /* Careful, do not re-install handlers we already installed */
    if (G.special_sig_mask != mask) {
        unsigned diff = mask & ~G.special_sig_mask;
        G.special_sig_mask = mask;
        install_sighandlers(diff);
    }
}

#if ENABLE_HUSH_JOB
/* helper */
/* Set handlers to restore tty pgrp and exit */
static void install_fatal_sighandlers(void)
{
    unsigned mask;

    /* We will restore tty pgrp on these signals */
    mask = 0
        + (1 << SIGILL ) * HUSH_DEBUG
        + (1 << SIGFPE ) * HUSH_DEBUG
        + (1 << SIGBUS ) * HUSH_DEBUG
        + (1 << SIGSEGV) * HUSH_DEBUG
        + (1 << SIGTRAP) * HUSH_DEBUG
        + (1 << SIGABRT)
    /* bash 3.2 seems to handle these just like 'fatal' ones */
        + (1 << SIGPIPE)
        + (1 << SIGALRM)
    /* if we are interactive, SIGHUP, SIGTERM and SIGINT are special sigs.
     * if we aren't interactive... but in this case
     * we never want to restore pgrp on exit, and this fn is not called
     */
        /*+ (1 << SIGHUP )*/
        /*+ (1 << SIGTERM)*/
        /*+ (1 << SIGINT )*/
    ;
    G_fatal_sig_mask = mask;

    install_sighandlers(mask);
}
#endif

static int set_mode(int state, char mode, const char *o_opt)
{
    int idx;
    switch (mode) {
    case 'n':
        G.o_opt[OPT_O_NOEXEC] = state;
        break;
    case 'x':
        IF_HUSH_MODE_X(G_x_mode = state;)
        break;
    case 'o':
        if (!o_opt) {
            /* "set -+o" without parameter.
             * in bash, set -o produces this output:
             *  pipefail        off
             * and set +o:
             *  set +o pipefail
             * We always use the second form.
             */
            const char *p = o_opt_strings;
            idx = 0;
            while (*p) {
                printf("set %co %s\n", (G.o_opt[idx] ? '-' : '+'), p);
                idx++;
                p += strlen(p) + 1;
            }
            break;
        }
        idx = index_in_strings(o_opt_strings, o_opt);
        if (idx >= 0) {
            G.o_opt[idx] = state;
            break;
        }
    default:
        return EXIT_FAILURE;
    }
    return EXIT_SUCCESS;
}

int hush_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int hush_main(int argc, char **argv)
{
    enum {
        OPT_login = (1 << 0),
    };
    unsigned flags;
    int opt;
    unsigned builtin_argc;
    char **e;
    struct variable *cur_var;
    struct variable *shell_ver;

    INIT_G();
    if (EXIT_SUCCESS != 0) /* if EXIT_SUCCESS == 0, it is already done */
        G.last_exitcode = EXIT_SUCCESS;

#if ENABLE_HUSH_FAST
    G.count_SIGCHLD++; /* ensure it is != G.handled_SIGCHLD */
#endif
#if !BB_MMU
    G.argv0_for_re_execing = argv[0];
#endif
    /* Deal with HUSH_VERSION */
    shell_ver = xzalloc(sizeof(*shell_ver));
    shell_ver->flg_export = 1;
    shell_ver->flg_read_only = 1;
    /* Code which handles ${var<op>...} needs writable values for all variables,
     * therefore we xstrdup: */
    shell_ver->varstr = xstrdup(hush_version_str);
    /* Create shell local variables from the values
     * currently living in the environment */
    debug_printf_env("unsetenv '%s'\n", "HUSH_VERSION");
    unsetenv("HUSH_VERSION"); /* in case it exists in initial env */
    G.top_var = shell_ver;
    cur_var = G.top_var;
    e = environ;
    if (e) while (*e) {
        char *value = strchr(*e, '=');
        if (value) { /* paranoia */
            cur_var->next = xzalloc(sizeof(*cur_var));
            cur_var = cur_var->next;
            cur_var->varstr = *e;
            cur_var->max_len = strlen(*e);
            cur_var->flg_export = 1;
        }
        e++;
    }
    /* (Re)insert HUSH_VERSION into env (AFTER we scanned the env!) */
    debug_printf_env("putenv '%s'\n", shell_ver->varstr);
    putenv(shell_ver->varstr);

    /* Export PWD */
    set_pwd_var(/*exp:*/ 1);

#if ENABLE_HUSH_BASH_COMPAT
    /* Set (but not export) HOSTNAME unless already set */
    if (!get_local_var_value("HOSTNAME")) {
        struct utsname uts;
        uname(&uts);
        set_local_var_from_halves("HOSTNAME", uts.nodename);
    }
    /* bash also exports SHLVL and _,
     * and sets (but doesn't export) the following variables:
     * BASH=/bin/bash
     * BASH_VERSINFO=([0]="3" [1]="2" [2]="0" [3]="1" [4]="release" [5]="i386-pc-linux-gnu")
     * BASH_VERSION='3.2.0(1)-release'
     * HOSTTYPE=i386
     * MACHTYPE=i386-pc-linux-gnu
     * OSTYPE=linux-gnu
     * PPID=<NNNNN> - we also do it elsewhere
     * EUID=<NNNNN>
     * UID=<NNNNN>
     * GROUPS=()
     * LINES=<NNN>
     * COLUMNS=<NNN>
     * BASH_ARGC=()
     * BASH_ARGV=()
     * BASH_LINENO=()
     * BASH_SOURCE=()
     * DIRSTACK=()
     * PIPESTATUS=([0]="0")
     * HISTFILE=/<xxx>/.bash_history
     * HISTFILESIZE=500
     * HISTSIZE=500
     * MAILCHECK=60
     * PATH=/usr/gnu/bin:/usr/local/bin:/bin:/usr/bin:.
     * SHELL=/bin/bash
     * SHELLOPTS=braceexpand:emacs:hashall:histexpand:history:interactive-comments:monitor
     * TERM=dumb
     * OPTERR=1
     * OPTIND=1
     * IFS=$' \t\n'
     * PS1='\s-\v\$ '
     * PS2='> '
     * PS4='+ '
     */
#endif

#if ENABLE_FEATURE_EDITING
    G.line_input_state = new_line_input_t(FOR_SHELL);
#endif

    /* Initialize some more globals to non-zero values */
    cmdedit_update_prompt();

    die_func = restore_ttypgrp_and__exit;

    /* Shell is non-interactive at first. We need to call
     * install_special_sighandlers() if we are going to execute "sh <script>",
     * "sh -c <cmds>" or login shell's /etc/profile and friends.
     * If we later decide that we are interactive, we run install_special_sighandlers()
     * in order to intercept (more) signals.
     */

    /* Parse options */
    /* http://www.opengroup.org/onlinepubs/9699919799/utilities/sh.html */
    flags = (argv[0] && argv[0][0] == '-') ? OPT_login : 0;
    builtin_argc = 0;
    while (1) {
        opt = getopt(argc, argv, "+c:xinsl"
#if !BB_MMU
                "<:$:R:V:"
# if ENABLE_HUSH_FUNCTIONS
                "F:"
# endif
#endif
        );
        if (opt <= 0)
            break;
        switch (opt) {
        case 'c':
            /* Possibilities:
             * sh ... -c 'script'
             * sh ... -c 'script' ARG0 [ARG1...]
             * On NOMMU, if builtin_argc != 0,
             * sh ... -c 'builtin' BARGV... "" ARG0 [ARG1...]
             * "" needs to be replaced with NULL
             * and BARGV vector fed to builtin function.
             * Note: the form without ARG0 never happens:
             * sh ... -c 'builtin' BARGV... ""
             */
            if (!G.root_pid) {
                G.root_pid = getpid();
                G.root_ppid = getppid();
            }
            G.global_argv = argv + optind;
            G.global_argc = argc - optind;
            if (builtin_argc) {
                /* -c 'builtin' [BARGV...] "" ARG0 [ARG1...] */
                const struct built_in_command *x;

                install_special_sighandlers();
                x = find_builtin(optarg);
                if (x) { /* paranoia */
                    G.global_argc -= builtin_argc; /* skip [BARGV...] "" */
                    G.global_argv += builtin_argc;
                    G.global_argv[-1] = NULL; /* replace "" */
                    fflush_all();
                    G.last_exitcode = x->b_function(argv + optind - 1);
                }
                goto final_return;
            }
            if (!G.global_argv[0]) {
                /* -c 'script' (no params): prevent empty $0 */
                G.global_argv--; /* points to argv[i] of 'script' */
                G.global_argv[0] = argv[0];
                G.global_argc++;
            } /* else -c 'script' ARG0 [ARG1...]: $0 is ARG0 */
            install_special_sighandlers();
            parse_and_run_string(optarg);
            goto final_return;
        case 'i':
            /* Well, we cannot just declare interactiveness,
             * we have to have some stuff (ctty, etc) */
            /* G_interactive_fd++; */
            break;
        case 's':
            /* "-s" means "read from stdin", but this is how we always
             * operate, so simply do nothing here. */
            break;
        case 'l':
            flags |= OPT_login;
            break;
#if !BB_MMU
        case '<': /* "big heredoc" support */
            full_write1_str(optarg);
            _exit(0);
        case '$': {
            unsigned long long empty_trap_mask;

            G.root_pid = bb_strtou(optarg, &optarg, 16);
            optarg++;
            G.root_ppid = bb_strtou(optarg, &optarg, 16);
            optarg++;
            G.last_bg_pid = bb_strtou(optarg, &optarg, 16);
            optarg++;
            G.last_exitcode = bb_strtou(optarg, &optarg, 16);
            optarg++;
            builtin_argc = bb_strtou(optarg, &optarg, 16);
            optarg++;
            empty_trap_mask = bb_strtoull(optarg, &optarg, 16);
            if (empty_trap_mask != 0) {
                int sig;
                install_special_sighandlers();
                G.traps = xzalloc(sizeof(G.traps[0]) * NSIG);
                for (sig = 1; sig < NSIG; sig++) {
                    if (empty_trap_mask & (1LL << sig)) {
                        G.traps[sig] = xzalloc(1); /* == xstrdup(""); */
                        install_sighandler(sig, SIG_IGN);
                    }
                }
            }
# if ENABLE_HUSH_LOOPS
            optarg++;
            G.depth_of_loop = bb_strtou(optarg, &optarg, 16);
# endif
            break;
        }
        case 'R':
        case 'V':
            set_local_var(xstrdup(optarg), /*exp:*/ 0, /*lvl:*/ 0, /*ro:*/ opt == 'R');
            break;
# if ENABLE_HUSH_FUNCTIONS
        case 'F': {
            struct function *funcp = new_function(optarg);
            /* funcp->name is already set to optarg */
            /* funcp->body is set to NULL. It's a special case. */
            funcp->body_as_string = argv[optind];
            optind++;
            break;
        }
# endif
#endif
        case 'n':
        case 'x':
            if (set_mode(1, opt, NULL) == 0) /* no error */
                break;
        default:
#ifndef BB_VER
            fprintf(stderr, "Usage: sh [FILE]...\n"
                    "   or: sh -c command [args]...\n\n");
            exit(EXIT_FAILURE);
#else
            bb_show_usage();
#endif
        }
    } /* option parsing loop */

    /* Skip options. Try "hush -l": $1 should not be "-l"! */
    G.global_argc = argc - (optind - 1);
    G.global_argv = argv + (optind - 1);
    G.global_argv[0] = argv[0];

    if (!G.root_pid) {
        G.root_pid = getpid();
        G.root_ppid = getppid();
    }

    /* If we are login shell... */
    if (flags & OPT_login) {
        FILE *input;
        debug_printf("sourcing /etc/profile\n");
        input = fopen_for_read("/etc/profile");
        if (input != NULL) {
            close_on_exec_on(fileno(input));
            install_special_sighandlers();
            parse_and_run_file(input);
            fclose(input);
        }
        /* bash: after sourcing /etc/profile,
         * tries to source (in the given order):
         * ~/.bash_profile, ~/.bash_login, ~/.profile,
         * stopping on first found. --noprofile turns this off.
         * bash also sources ~/.bash_logout on exit.
         * If called as sh, skips .bash_XXX files.
         */
    }

    if (G.global_argv[1]) {
        FILE *input;
        /*
         * "bash <script>" (which is never interactive (unless -i?))
         * sources $BASH_ENV here (without scanning $PATH).
         * If called as sh, does the same but with $ENV.
         */
        G.global_argc--;
        G.global_argv++;
        debug_printf("running script '%s'\n", G.global_argv[0]);
        input = xfopen_for_read(G.global_argv[0]);
        close_on_exec_on(fileno(input));
        install_special_sighandlers();
        parse_and_run_file(input);
#if ENABLE_FEATURE_CLEAN_UP
        fclose(input);
#endif
        goto final_return;
    }

    /* Up to here, shell was non-interactive. Now it may become one.
     * NB: don't forget to (re)run install_special_sighandlers() as needed.
     */

    /* A shell is interactive if the '-i' flag was given,
     * or if all of the following conditions are met:
     *    no -c command
     *    no arguments remaining or the -s flag given
     *    standard input is a terminal
     *    standard output is a terminal
     * Refer to Posix.2, the description of the 'sh' utility.
     */
#if ENABLE_HUSH_JOB
    if (isatty(STDIN_FILENO) && isatty(STDOUT_FILENO)) {
        G_saved_tty_pgrp = tcgetpgrp(STDIN_FILENO);
        debug_printf("saved_tty_pgrp:%d\n", G_saved_tty_pgrp);
        if (G_saved_tty_pgrp < 0)
            G_saved_tty_pgrp = 0;

        /* try to dup stdin to high fd#, >= 255 */
        G_interactive_fd = fcntl(STDIN_FILENO, F_DUPFD, 255);
        if (G_interactive_fd < 0) {
            /* try to dup to any fd */
            G_interactive_fd = dup(STDIN_FILENO);
            if (G_interactive_fd < 0) {
                /* give up */
                G_interactive_fd = 0;
                G_saved_tty_pgrp = 0;
            }
        }
// TODO: track & disallow any attempts of user
// to (inadvertently) close/redirect G_interactive_fd
    }
    debug_printf("interactive_fd:%d\n", G_interactive_fd);
    if (G_interactive_fd) {
        close_on_exec_on(G_interactive_fd);

        if (G_saved_tty_pgrp) {
            /* If we were run as 'hush &', sleep until we are
             * in the foreground (tty pgrp == our pgrp).
             * If we get started under a job aware app (like bash),
             * make sure we are now in charge so we don't fight over
             * who gets the foreground */
            while (1) {
                pid_t shell_pgrp = getpgrp();
                G_saved_tty_pgrp = tcgetpgrp(G_interactive_fd);
                if (G_saved_tty_pgrp == shell_pgrp)
                    break;
                /* send TTIN to ourself (should stop us) */
                kill(- shell_pgrp, SIGTTIN);
            }
        }

        /* Install more signal handlers */
        install_special_sighandlers();

        if (G_saved_tty_pgrp) {
            /* Set other signals to restore saved_tty_pgrp */
            install_fatal_sighandlers();
            /* Put ourselves in our own process group
             * (bash, too, does this only if ctty is available) */
            bb_setpgrp(); /* is the same as setpgid(our_pid, our_pid); */
            /* Grab control of the terminal */
            tcsetpgrp(G_interactive_fd, getpid());
        }
        enable_restore_tty_pgrp_on_exit();

# if ENABLE_HUSH_SAVEHISTORY && MAX_HISTORY > 0
        {
            const char *hp = get_local_var_value("HISTFILE");
            if (!hp) {
                hp = get_local_var_value("HOME");
                if (hp)
                    hp = concat_path_file(hp, ".hush_history");
            } else {
                hp = xstrdup(hp);
            }
            if (hp) {
                G.line_input_state->hist_file = hp;
                //set_local_var(xasprintf("HISTFILE=%s", ...));
            }
#  if ENABLE_FEATURE_SH_HISTFILESIZE
            hp = get_local_var_value("HISTFILESIZE");
            G.line_input_state->max_history = size_from_HISTFILESIZE(hp);
#  endif
        }
# endif
    } else {
        install_special_sighandlers();
    }
#elif ENABLE_HUSH_INTERACTIVE
    /* No job control compiled in, only prompt/line editing */
    if (isatty(STDIN_FILENO) && isatty(STDOUT_FILENO)) {
        G_interactive_fd = fcntl(STDIN_FILENO, F_DUPFD, 255);
        if (G_interactive_fd < 0) {
            /* try to dup to any fd */
            G_interactive_fd = dup(STDIN_FILENO);
            if (G_interactive_fd < 0)
                /* give up */
                G_interactive_fd = 0;
        }
    }
    if (G_interactive_fd) {
        close_on_exec_on(G_interactive_fd);
    }
    install_special_sighandlers();
#else
    /* We have interactiveness code disabled */
    install_special_sighandlers();
#endif
    /* bash:
     * if interactive but not a login shell, sources ~/.bashrc
     * (--norc turns this off, --rcfile <file> overrides)
     */

    if (!ENABLE_FEATURE_SH_EXTRA_QUIET && G_interactive_fd) {
        /* note: ash and hush share this string */
        printf("\n\n%s %s\n"
            IF_HUSH_HELP("Enter 'help' for a list of built-in commands.\n")
            "\n",
            bb_banner,
            "hush - the humble shell"
        );
    }

    parse_and_run_file(stdin);

 final_return:
    hush_exit(G.last_exitcode);
}


#if ENABLE_MSH
int msh_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int msh_main(int argc, char **argv)
{
    //bb_error_msg("msh is deprecated, please use hush instead");
    return hush_main(argc, argv);
}
#endif


/*
 * Built-ins
 */
static int FAST_FUNC builtin_true(char **argv UNUSED_PARAM)
{
    return 0;
}

static int run_applet_main(char **argv, int (*applet_main_func)(int argc, char **argv))
{
    int argc = 0;
    while (*argv) {
        argc++;
        argv++;
    }
    return applet_main_func(argc, argv - argc);
}

static int FAST_FUNC builtin_test(char **argv)
{
    return run_applet_main(argv, test_main);
}

static int FAST_FUNC builtin_echo(char **argv)
{
    return run_applet_main(argv, echo_main);
}

#if ENABLE_PRINTF
static int FAST_FUNC builtin_printf(char **argv)
{
    return run_applet_main(argv, printf_main);
}
#endif

static char **skip_dash_dash(char **argv)
{
    argv++;
    if (argv[0] && argv[0][0] == '-' && argv[0][1] == '-' && argv[0][2] == '\0')
        argv++;
    return argv;
}

static int FAST_FUNC builtin_eval(char **argv)
{
    int rcode = EXIT_SUCCESS;

    argv = skip_dash_dash(argv);
    if (*argv) {
        char *str = expand_strvec_to_string(argv);
        /* bash:
         * eval "echo Hi; done" ("done" is syntax error):
         * "echo Hi" will not execute too.
         */
        parse_and_run_string(str);
        free(str);
        rcode = G.last_exitcode;
    }
    return rcode;
}

static int FAST_FUNC builtin_cd(char **argv)
{
    const char *newdir;

    argv = skip_dash_dash(argv);
    newdir = argv[0];
    if (newdir == NULL) {
        /* bash does nothing (exitcode 0) if HOME is ""; if it's unset,
         * bash says "bash: cd: HOME not set" and does nothing
         * (exitcode 1)
         */
        const char *home = get_local_var_value("HOME");
        newdir = home ? home : "/";
    }
    if (chdir(newdir)) {
        /* Mimic bash message exactly */
        bb_perror_msg("cd: %s", newdir);
        return EXIT_FAILURE;
    }
    /* Read current dir (get_cwd(1) is inside) and set PWD.
     * Note: do not enforce exporting. If PWD was unset or unexported,
     * set it again, but do not export. bash does the same.
     */
    set_pwd_var(/*exp:*/ 0);
    return EXIT_SUCCESS;
}

static int FAST_FUNC builtin_exec(char **argv)
{
    argv = skip_dash_dash(argv);
    if (argv[0] == NULL)
        return EXIT_SUCCESS; /* bash does this */

    /* Careful: we can end up here after [v]fork. Do not restore
     * tty pgrp then, only top-level shell process does that */
    if (G_saved_tty_pgrp && getpid() == G.root_pid)
        tcsetpgrp(G_interactive_fd, G_saved_tty_pgrp);

    /* TODO: if exec fails, bash does NOT exit! We do.
     * We'll need to undo trap cleanup (it's inside execvp_or_die)
     * and tcsetpgrp, and this is inherently racy.
     */
    execvp_or_die(argv);
}

static int FAST_FUNC builtin_exit(char **argv)
{
    debug_printf_exec("%s()\n", __func__);

    /* interactive bash:
     * # trap "echo EEE" EXIT
     * # exit
     * exit
     * There are stopped jobs.
     * (if there are _stopped_ jobs, running ones don't count)
     * # exit
     * exit
     * EEE (then bash exits)
     *
     * TODO: we can use G.exiting = -1 as indicator "last cmd was exit"
     */

    /* note: EXIT trap is run by hush_exit */
    argv = skip_dash_dash(argv);
    if (argv[0] == NULL)
        hush_exit(G.last_exitcode);
    /* mimic bash: exit 123abc == exit 255 + error msg */
    xfunc_error_retval = 255;
    /* bash: exit -2 == exit 254, no error msg */
    hush_exit(xatoi(argv[0]) & 0xff);
}

static void print_escaped(const char *s)
{
    if (*s == '\'')
        goto squote;
    do {
        const char *p = strchrnul(s, '\'');
        /* print 'xxxx', possibly just '' */
        printf("'%.*s'", (int)(p - s), s);
        if (*p == '\0')
            break;
        s = p;
 squote:
        /* s points to '; print "'''...'''" */
        putchar('"');
        do putchar('\''); while (*++s == '\'');
        putchar('"');
    } while (*s);
}

#if !ENABLE_HUSH_LOCAL
#define helper_export_local(argv, exp, lvl) \
    helper_export_local(argv, exp)
#endif
static void helper_export_local(char **argv, int exp, int lvl)
{
    do {
        char *name = *argv;
        char *name_end = strchrnul(name, '=');

        /* So far we do not check that name is valid (TODO?) */

        if (*name_end == '\0') {
            struct variable *var, **vpp;

            vpp = get_ptr_to_local_var(name, name_end - name);
            var = vpp ? *vpp : NULL;

            if (exp == -1) { /* unexporting? */
                /* export -n NAME (without =VALUE) */
                if (var) {
                    var->flg_export = 0;
                    debug_printf_env("%s: unsetenv '%s'\n", __func__, name);
                    unsetenv(name);
                } /* else: export -n NOT_EXISTING_VAR: no-op */
                continue;
            }
            if (exp == 1) { /* exporting? */
                /* export NAME (without =VALUE) */
                if (var) {
                    var->flg_export = 1;
                    debug_printf_env("%s: putenv '%s'\n", __func__, var->varstr);
                    putenv(var->varstr);
                    continue;
                }
            }
            /* Exporting non-existing variable.
             * bash does not put it in environment,
             * but remembers that it is exported,
             * and does put it in env when it is set later.
             * We just set it to "" and export. */
            /* Or, it's "local NAME" (without =VALUE).
             * bash sets the value to "". */
            name = xasprintf("%s=", name);
        } else {
            /* (Un)exporting/making local NAME=VALUE */
            name = xstrdup(name);
        }
        set_local_var(name, /*exp:*/ exp, /*lvl:*/ lvl, /*ro:*/ 0);
    } while (*++argv);
}

static int FAST_FUNC builtin_export(char **argv)
{
    unsigned opt_unexport;

#if ENABLE_HUSH_EXPORT_N
    /* "!": do not abort on errors */
    opt_unexport = getopt32(argv, "!n");
    if (opt_unexport == (uint32_t)-1)
        return EXIT_FAILURE;
    argv += optind;
#else
    opt_unexport = 0;
    argv++;
#endif

    if (argv[0] == NULL) {
        char **e = environ;
        if (e) {
            while (*e) {
#if 0
                puts(*e++);
#else
                /* ash emits: export VAR='VAL'
                 * bash: declare -x VAR="VAL"
                 * we follow ash example */
                const char *s = *e++;
                const char *p = strchr(s, '=');

                if (!p) /* wtf? take next variable */
                    continue;
                /* export var= */
                printf("export %.*s", (int)(p - s) + 1, s);
                print_escaped(p + 1);
                putchar('\n');
#endif
            }
            /*fflush_all(); - done after each builtin anyway */
        }
        return EXIT_SUCCESS;
    }

    helper_export_local(argv, (opt_unexport ? -1 : 1), 0);

    return EXIT_SUCCESS;
}

#if ENABLE_HUSH_LOCAL
static int FAST_FUNC builtin_local(char **argv)
{
    if (G.func_nest_level == 0) {
        bb_error_msg("%s: not in a function", argv[0]);
        return EXIT_FAILURE; /* bash compat */
    }
    helper_export_local(argv, 0, G.func_nest_level);
    return EXIT_SUCCESS;
}
#endif

static int FAST_FUNC builtin_trap(char **argv)
{
    int sig;
    char *new_cmd;

    if (!G.traps)
        G.traps = xzalloc(sizeof(G.traps[0]) * NSIG);

    argv++;
    if (!*argv) {
        int i;
        /* No args: print all trapped */
        for (i = 0; i < NSIG; ++i) {
            if (G.traps[i]) {
                printf("trap -- ");
                print_escaped(G.traps[i]);
                /* note: bash adds "SIG", but only if invoked
                 * as "bash". If called as "sh", or if set -o posix,
                 * then it prints short signal names.
                 * We are printing short names: */
                printf(" %s\n", get_signame(i));
            }
        }
        /*fflush_all(); - done after each builtin anyway */
        return EXIT_SUCCESS;
    }

    new_cmd = NULL;
    /* If first arg is a number: reset all specified signals */
    sig = bb_strtou(*argv, NULL, 10);
    if (errno == 0) {
        int ret;
 process_sig_list:
        ret = EXIT_SUCCESS;
        while (*argv) {
            sighandler_t handler;

            sig = get_signum(*argv++);
            if (sig < 0 || sig >= NSIG) {
                ret = EXIT_FAILURE;
                /* Mimic bash message exactly */
                bb_perror_msg("trap: %s: invalid signal specification", argv[-1]);
                continue;
            }

            free(G.traps[sig]);
            G.traps[sig] = xstrdup(new_cmd);

            debug_printf("trap: setting SIG%s (%i) to '%s'\n",
                get_signame(sig), sig, G.traps[sig]);

            /* There is no signal for 0 (EXIT) */
            if (sig == 0)
                continue;

            if (new_cmd)
                handler = (new_cmd[0] ? record_pending_signo : SIG_IGN);
            else
                /* We are removing trap handler */
                handler = pick_sighandler(sig);
            install_sighandler(sig, handler);
        }
        return ret;
    }

    if (!argv[1]) { /* no second arg */
        bb_error_msg("trap: invalid arguments");
        return EXIT_FAILURE;
    }

    /* First arg is "-": reset all specified to default */
    /* First arg is "--": skip it, the rest is "handler SIGs..." */
    /* Everything else: set arg as signal handler
     * (includes "" case, which ignores signal) */
    if (argv[0][0] == '-') {
        if (argv[0][1] == '\0') { /* "-" */
            /* new_cmd remains NULL: "reset these sigs" */
            goto reset_traps;
        }
        if (argv[0][1] == '-' && argv[0][2] == '\0') { /* "--" */
            argv++;
        }
        /* else: "-something", no special meaning */
    }
    new_cmd = *argv;
 reset_traps:
    argv++;
    goto process_sig_list;
}

/* http://www.opengroup.org/onlinepubs/9699919799/utilities/type.html */
static int FAST_FUNC builtin_type(char **argv)
{
    int ret = EXIT_SUCCESS;

    while (*++argv) {
        const char *type;
        char *path = NULL;

        if (0) {} /* make conditional compile easier below */
        /*else if (find_alias(*argv))
            type = "an alias";*/
#if ENABLE_HUSH_FUNCTIONS
        else if (find_function(*argv))
            type = "a function";
#endif
        else if (find_builtin(*argv))
            type = "a shell builtin";
        else if ((path = find_in_path(*argv)) != NULL)
            type = path;
        else {
            bb_error_msg("type: %s: not found", *argv);
            ret = EXIT_FAILURE;
            continue;
        }

        printf("%s is %s\n", *argv, type);
        free(path);
    }

    return ret;
}

#if ENABLE_HUSH_JOB
/* built-in 'fg' and 'bg' handler */
static int FAST_FUNC builtin_fg_bg(char **argv)
{
    int i, jobnum;
    struct pipe *pi;

    if (!G_interactive_fd)
        return EXIT_FAILURE;

    /* If they gave us no args, assume they want the last backgrounded task */
    if (!argv[1]) {
        for (pi = G.job_list; pi; pi = pi->next) {
            if (pi->jobid == G.last_jobid) {
                goto found;
            }
        }
        bb_error_msg("%s: no current job", argv[0]);
        return EXIT_FAILURE;
    }
    if (sscanf(argv[1], "%%%d", &jobnum) != 1) {
        bb_error_msg("%s: bad argument '%s'", argv[0], argv[1]);
        return EXIT_FAILURE;
    }
    for (pi = G.job_list; pi; pi = pi->next) {
        if (pi->jobid == jobnum) {
            goto found;
        }
    }
    bb_error_msg("%s: %d: no such job", argv[0], jobnum);
    return EXIT_FAILURE;
 found:
    /* TODO: bash prints a string representation
     * of job being foregrounded (like "sleep 1 | cat") */
    if (argv[0][0] == 'f' && G_saved_tty_pgrp) {
        /* Put the job into the foreground.  */
        tcsetpgrp(G_interactive_fd, pi->pgrp);
    }

    /* Restart the processes in the job */
    debug_printf_jobs("reviving %d procs, pgrp %d\n", pi->num_cmds, pi->pgrp);
    for (i = 0; i < pi->num_cmds; i++) {
        debug_printf_jobs("reviving pid %d\n", pi->cmds[i].pid);
    }
    pi->stopped_cmds = 0;

    i = kill(- pi->pgrp, SIGCONT);
    if (i < 0) {
        if (errno == ESRCH) {
            delete_finished_bg_job(pi);
            return EXIT_SUCCESS;
        }
        bb_perror_msg("kill (SIGCONT)");
    }

    if (argv[0][0] == 'f') {
        remove_bg_job(pi);
        return checkjobs_and_fg_shell(pi);
    }
    return EXIT_SUCCESS;
}
#endif

#if ENABLE_HUSH_HELP
static int FAST_FUNC builtin_help(char **argv UNUSED_PARAM)
{
    const struct built_in_command *x;

    printf(
        "Built-in commands:\n"
        "------------------\n");
    for (x = bltins1; x != &bltins1[ARRAY_SIZE(bltins1)]; x++) {
        if (x->b_descr)
            printf("%-10s%s\n", x->b_cmd, x->b_descr);
    }
    bb_putchar('\n');
    return EXIT_SUCCESS;
}
#endif

#if MAX_HISTORY && ENABLE_FEATURE_EDITING
static int FAST_FUNC builtin_history(char **argv UNUSED_PARAM)
{
    show_history(G.line_input_state);
    return EXIT_SUCCESS;
}
#endif

#if ENABLE_HUSH_JOB
static int FAST_FUNC builtin_jobs(char **argv UNUSED_PARAM)
{
    struct pipe *job;
    const char *status_string;

    for (job = G.job_list; job; job = job->next) {
        if (job->alive_cmds == job->stopped_cmds)
            status_string = "Stopped";
        else
            status_string = "Running";

        printf(JOB_STATUS_FORMAT, job->jobid, status_string, job->cmdtext);
    }
    return EXIT_SUCCESS;
}
#endif

#if HUSH_DEBUG
static int FAST_FUNC builtin_memleak(char **argv UNUSED_PARAM)
{
    void *p;
    unsigned long l;

# ifdef M_TRIM_THRESHOLD
    /* Optional. Reduces probability of false positives */
    malloc_trim(0);
# endif
    /* Crude attempt to find where "free memory" starts,
     * sans fragmentation. */
    p = malloc(240);
    l = (unsigned long)p;
    free(p);
    p = malloc(3400);
    if (l < (unsigned long)p) l = (unsigned long)p;
    free(p);

    if (!G.memleak_value)
        G.memleak_value = l;

    l -= G.memleak_value;
    if ((long)l < 0)
        l = 0;
    l /= 1024;
    if (l > 127)
        l = 127;

    /* Exitcode is "how many kilobytes we leaked since 1st call" */
    return l;
}
#endif

static int FAST_FUNC builtin_pwd(char **argv UNUSED_PARAM)
{
    puts(get_cwd(0));
    return EXIT_SUCCESS;
}

/* Interruptibility of read builtin in bash
 * (tested on bash-4.2.8 by sending signals (not by ^C)):
 *
 * Empty trap makes read ignore corresponding signal, for any signal.
 *
 * SIGINT:
 * - terminates non-interactive shell;
 * - interrupts read in interactive shell;
 * if it has non-empty trap:
 * - executes trap and returns to command prompt in interactive shell;
 * - executes trap and returns to read in non-interactive shell;
 * SIGTERM:
 * - is ignored (does not interrupt) read in interactive shell;
 * - terminates non-interactive shell;
 * if it has non-empty trap:
 * - executes trap and returns to read;
 * SIGHUP:
 * - terminates shell (regardless of interactivity);
 * if it has non-empty trap:
 * - executes trap and returns to read;
 */
static int FAST_FUNC builtin_read(char **argv)
{
    const char *r;
    char *opt_n = NULL;
    char *opt_p = NULL;
    char *opt_t = NULL;
    char *opt_u = NULL;
    const char *ifs;
    int read_flags;

    /* "!": do not abort on errors.
     * Option string must start with "sr" to match BUILTIN_READ_xxx
     */
    read_flags = getopt32(argv, "!srn:p:t:u:", &opt_n, &opt_p, &opt_t, &opt_u);
    if (read_flags == (uint32_t)-1)
        return EXIT_FAILURE;
    argv += optind;
    ifs = get_local_var_value("IFS"); /* can be NULL */

 again:
    r = shell_builtin_read(set_local_var_from_halves,
        argv,
        ifs,
        read_flags,
        opt_n,
        opt_p,
        opt_t,
        opt_u
    );

    if ((uintptr_t)r == 1 && errno == EINTR) {
        unsigned sig = check_and_run_traps();
        if (sig && sig != SIGINT)
            goto again;
    }

    if ((uintptr_t)r > 1) {
        bb_error_msg("%s", r);
        r = (char*)(uintptr_t)1;
    }

    return (uintptr_t)r;
}

/* http://www.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#set
 * built-in 'set' handler
 * SUSv3 says:
 * set [-abCefhmnuvx] [-o option] [argument...]
 * set [+abCefhmnuvx] [+o option] [argument...]
 * set -- [argument...]
 * set -o
 * set +o
 * Implementations shall support the options in both their hyphen and
 * plus-sign forms. These options can also be specified as options to sh.
 * Examples:
 * Write out all variables and their values: set
 * Set $1, $2, and $3 and set "$#" to 3: set c a b
 * Turn on the -x and -v options: set -xv
 * Unset all positional parameters: set --
 * Set $1 to the value of x, even if it begins with '-' or '+': set -- "$x"
 * Set the positional parameters to the expansion of x, even if x expands
 * with a leading '-' or '+': set -- $x
 *
 * So far, we only support "set -- [argument...]" and some of the short names.
 */
static int FAST_FUNC builtin_set(char **argv)
{
    int n;
    char **pp, **g_argv;
    char *arg = *++argv;

    if (arg == NULL) {
        struct variable *e;
        for (e = G.top_var; e; e = e->next)
            puts(e->varstr);
        return EXIT_SUCCESS;
    }

    do {
        if (strcmp(arg, "--") == 0) {
            ++argv;
            goto set_argv;
        }
        if (arg[0] != '+' && arg[0] != '-')
            break;
        for (n = 1; arg[n]; ++n) {
            if (set_mode((arg[0] == '-'), arg[n], argv[1]))
                goto error;
            if (arg[n] == 'o' && argv[1])
                argv++;
        }
    } while ((arg = *++argv) != NULL);
    /* Now argv[0] is 1st argument */

    if (arg == NULL)
        return EXIT_SUCCESS;
 set_argv:

    /* NB: G.global_argv[0] ($0) is never freed/changed */
    g_argv = G.global_argv;
    if (G.global_args_malloced) {
        pp = g_argv;
        while (*++pp)
            free(*pp);
        g_argv[1] = NULL;
    } else {
        G.global_args_malloced = 1;
        pp = xzalloc(sizeof(pp[0]) * 2);
        pp[0] = g_argv[0]; /* retain $0 */
        g_argv = pp;
    }
    /* This realloc's G.global_argv */
    G.global_argv = pp = add_strings_to_strings(g_argv, argv, /*dup:*/ 1);

    n = 1;
    while (*++pp)
        n++;
    G.global_argc = n;

    return EXIT_SUCCESS;

    /* Nothing known, so abort */
 error:
    bb_error_msg("set: %s: invalid option", arg);
    return EXIT_FAILURE;
}

static int FAST_FUNC builtin_shift(char **argv)
{
    int n = 1;
    argv = skip_dash_dash(argv);
    if (argv[0]) {
        n = atoi(argv[0]);
    }
    if (n >= 0 && n < G.global_argc) {
        if (G.global_args_malloced) {
            int m = 1;
            while (m <= n)
                free(G.global_argv[m++]);
        }
        G.global_argc -= n;
        memmove(&G.global_argv[1], &G.global_argv[n+1],
                G.global_argc * sizeof(G.global_argv[0]));
        return EXIT_SUCCESS;
    }
    return EXIT_FAILURE;
}

static int FAST_FUNC builtin_source(char **argv)
{
    char *arg_path, *filename;
    FILE *input;
    save_arg_t sv;
#if ENABLE_HUSH_FUNCTIONS
    smallint sv_flg;
#endif

    argv = skip_dash_dash(argv);
    filename = argv[0];
    if (!filename) {
        /* bash says: "bash: .: filename argument required" */
        return 2; /* bash compat */
    }
    arg_path = NULL;
    if (!strchr(filename, '/')) {
        arg_path = find_in_path(filename);
        if (arg_path)
            filename = arg_path;
    }
    input = fopen_or_warn(filename, "r");
    free(arg_path);
    if (!input) {
        /* bb_perror_msg("%s", *argv); - done by fopen_or_warn */
        /* POSIX: non-interactive shell should abort here,
         * not merely fail. So far no one complained :)
         */
        return EXIT_FAILURE;
    }
    close_on_exec_on(fileno(input));

#if ENABLE_HUSH_FUNCTIONS
    sv_flg = G.flag_return_in_progress;
    /* "we are inside sourced file, ok to use return" */
    G.flag_return_in_progress = -1;
#endif
    if (argv[1])
        save_and_replace_G_args(&sv, argv);

    parse_and_run_file(input);
    fclose(input);

    if (argv[1])
        restore_G_args(&sv, argv);
#if ENABLE_HUSH_FUNCTIONS
    G.flag_return_in_progress = sv_flg;
#endif

    return G.last_exitcode;
}

static int FAST_FUNC builtin_umask(char **argv)
{
    int rc;
    mode_t mask;

    rc = 1;
    mask = umask(0);
    argv = skip_dash_dash(argv);
    if (argv[0]) {
        mode_t old_mask = mask;

        /* numeric umasks are taken as-is */
        /* symbolic umasks are inverted: "umask a=rx" calls umask(222) */
        if (!isdigit(argv[0][0]))
            mask ^= 0777;
        mask = bb_parse_mode(argv[0], mask);
        if (!isdigit(argv[0][0]))
            mask ^= 0777;
        if ((unsigned)mask > 0777) {
            mask = old_mask;
            /* bash messages:
             * bash: umask: 'q': invalid symbolic mode operator
             * bash: umask: 999: octal number out of range
             */
            bb_error_msg("%s: invalid mode '%s'", "umask", argv[0]);
            rc = 0;
        }
    } else {
        /* Mimic bash */
        printf("%04o\n", (unsigned) mask);
        /* fall through and restore mask which we set to 0 */
    }
    umask(mask);

    return !rc; /* rc != 0 - success */
}

/* http://www.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#unset */
static int FAST_FUNC builtin_unset(char **argv)
{
    int ret;
    unsigned opts;

    /* "!": do not abort on errors */
    /* "+": stop at 1st non-option */
    opts = getopt32(argv, "!+vf");
    if (opts == (unsigned)-1)
        return EXIT_FAILURE;
    if (opts == 3) {
        bb_error_msg("unset: -v and -f are exclusive");
        return EXIT_FAILURE;
    }
    argv += optind;

    ret = EXIT_SUCCESS;
    while (*argv) {
        if (!(opts & 2)) { /* not -f */
            if (unset_local_var(*argv)) {
                /* unset <nonexistent_var> doesn't fail.
                 * Error is when one tries to unset RO var.
                 * Message was printed by unset_local_var. */
                ret = EXIT_FAILURE;
            }
        }
#if ENABLE_HUSH_FUNCTIONS
        else {
            unset_func(*argv);
        }
#endif
        argv++;
    }
    return ret;
}

/* http://www.opengroup.org/onlinepubs/9699919799/utilities/wait.html */
static int FAST_FUNC builtin_wait(char **argv)
{
    int ret = EXIT_SUCCESS;
    int status;

    argv = skip_dash_dash(argv);
    if (argv[0] == NULL) {
        /* Don't care about wait results */
        /* Note 1: must wait until there are no more children */
        /* Note 2: must be interruptible */
        /* Examples:
         * $ sleep 3 & sleep 6 & wait
         * [1] 30934 sleep 3
         * [2] 30935 sleep 6
         * [1] Done                   sleep 3
         * [2] Done                   sleep 6
         * $ sleep 3 & sleep 6 & wait
         * [1] 30936 sleep 3
         * [2] 30937 sleep 6
         * [1] Done                   sleep 3
         * ^C <-- after ~4 sec from keyboard
         * $
         */
        while (1) {
            int sig;
            sigset_t oldset, allsigs;

            /* waitpid is not interruptible by SA_RESTARTed
             * signals which we use. Thus, this ugly dance:
             */

            /* Make sure possible SIGCHLD is stored in kernel's
             * pending signal mask before we call waitpid.
             * Or else we may race with SIGCHLD, lose it,
             * and get stuck in sigwaitinfo...
             */
            sigfillset(&allsigs);
            sigprocmask(SIG_SETMASK, &allsigs, &oldset);

            if (!sigisemptyset(&G.pending_set)) {
                /* Crap! we raced with some signal! */
            //  sig = 0;
                goto restore;
            }

            checkjobs(NULL); /* waitpid(WNOHANG) inside */
            if (errno == ECHILD) {
                sigprocmask(SIG_SETMASK, &oldset, NULL);
                break;
            }

            /* Wait for SIGCHLD or any other signal */
            //sig = sigwaitinfo(&allsigs, NULL);
            /* It is vitally important for sigsuspend that SIGCHLD has non-DFL handler! */
            /* Note: sigsuspend invokes signal handler */
            sigsuspend(&oldset);
 restore:
            sigprocmask(SIG_SETMASK, &oldset, NULL);

            /* So, did we get a signal? */
            //if (sig > 0)
            //  raise(sig); /* run handler */
            sig = check_and_run_traps();
            if (sig /*&& sig != SIGCHLD - always true */) {
                /* see note 2 */
                ret = 128 + sig;
                break;
            }
            /* SIGCHLD, or no signal, or ignored one, such as SIGQUIT. Repeat */
        }
        return ret;
    }

    /* This is probably buggy wrt interruptible-ness */
    while (*argv) {
        pid_t pid = bb_strtou(*argv, NULL, 10);
        if (errno) {
            /* mimic bash message */
            bb_error_msg("wait: '%s': not a pid or valid job spec", *argv);
            return EXIT_FAILURE;
        }
        if (waitpid(pid, &status, 0) == pid) {
            ret = WEXITSTATUS(status);
            if (WIFSIGNALED(status))
                ret = 128 + WTERMSIG(status);
        } else {
            bb_perror_msg("wait %s", *argv);
            ret = 127;
        }
        argv++;
    }

    return ret;
}

#if ENABLE_HUSH_LOOPS || ENABLE_HUSH_FUNCTIONS
static unsigned parse_numeric_argv1(char **argv, unsigned def, unsigned def_min)
{
    if (argv[1]) {
        def = bb_strtou(argv[1], NULL, 10);
        if (errno || def < def_min || argv[2]) {
            bb_error_msg("%s: bad arguments", argv[0]);
            def = UINT_MAX;
        }
    }
    return def;
}
#endif

#if ENABLE_HUSH_LOOPS
static int FAST_FUNC builtin_break(char **argv)
{
    unsigned depth;
    if (G.depth_of_loop == 0) {
        bb_error_msg("%s: only meaningful in a loop", argv[0]);
        return EXIT_SUCCESS; /* bash compat */
    }
    G.flag_break_continue++; /* BC_BREAK = 1 */

    G.depth_break_continue = depth = parse_numeric_argv1(argv, 1, 1);
    if (depth == UINT_MAX)
        G.flag_break_continue = BC_BREAK;
    if (G.depth_of_loop < depth)
        G.depth_break_continue = G.depth_of_loop;

    return EXIT_SUCCESS;
}

static int FAST_FUNC builtin_continue(char **argv)
{
    G.flag_break_continue = 1; /* BC_CONTINUE = 2 = 1+1 */
    return builtin_break(argv);
}
#endif

#if ENABLE_HUSH_FUNCTIONS
static int FAST_FUNC builtin_return(char **argv)
{
    int rc;

    if (G.flag_return_in_progress != -1) {
        bb_error_msg("%s: not in a function or sourced script", argv[0]);
        return EXIT_FAILURE; /* bash compat */
    }

    G.flag_return_in_progress = 1;

    /* bash:
     * out of range: wraps around at 256, does not error out
     * non-numeric param:
     * f() { false; return qwe; }; f; echo $?
     * bash: return: qwe: numeric argument required  <== we do this
     * 255  <== we also do this
     */
    rc = parse_numeric_argv1(argv, G.last_exitcode, 0);
    return rc;
}
#endif