source: MondoRescue/branches/stable/mindi-busybox/editors/sed.c@ 821

/* vi: set sw=4 ts=4: */
/*
 * sed.c - very minimalist version of sed
 *
 * Copyright (C) 1999,2000,2001 by Lineo, inc. and Mark Whitley
 * Copyright (C) 1999,2000,2001 by Mark Whitley <markw@codepoet.org>
 * Copyright (C) 2002  Matt Kraai
 * Copyright (C) 2003 by Glenn McGrath <bug1@iinet.net.au>
 * Copyright (C) 2003,2004 by Rob Landley <rob@landley.net>
 *
 * MAINTAINER: Rob Landley <rob@landley.net>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
 */

/* Code overview.

  Files are laid out to avoid unnecessary function declarations.  So for
  example, every function add_cmd calls occurs before add_cmd in this file.

  add_cmd() is called on each line of sed command text (from a file or from
  the command line).  It calls get_address() and parse_cmd_args().  The
  resulting sed_cmd_t structures are appended to a linked list
  (bbg.sed_cmd_head/bbg.sed_cmd_tail).

  add_input_file() adds a FILE * to the list of input files.  We need to
  know all input sources ahead of time to find the last line for the $ match.

  process_files() does actual sedding, reading data lines from each input FILE *
  (which could be stdin) and applying the sed command list (sed_cmd_head) to
  each of the resulting lines.

  sed_main() is where external code calls into this, with a command line.
*/


/*
    Supported features and commands in this version of sed:

     - comments ('#')
     - address matching: num|/matchstr/[,num|/matchstr/|$]command
     - commands: (p)rint, (d)elete, (s)ubstitue (with g & I flags)
     - edit commands: (a)ppend, (i)nsert, (c)hange
     - file commands: (r)ead
     - backreferences in substitution expressions (\0, \1, \2...\9)
     - grouped commands: {cmd1;cmd2}
     - transliteration (y/source-chars/dest-chars/)
     - pattern space hold space storing / swapping (g, h, x)
     - labels / branching (: label, b, t, T)

     (Note: Specifying an address (range) to match is *optional*; commands
     default to the whole pattern space if no specific address match was
     requested.)

    Todo:
     - Create a wrapper around regex to make libc's regex conform with sed

    Reference http://www.opengroup.org/onlinepubs/007904975/utilities/sed.html
*/

#include <stdio.h>
#include <unistd.h>     /* for getopt() */
#include <errno.h>
#include <ctype.h>      /* for isspace() */
#include <stdlib.h>
#include <string.h>
#include "busybox.h"
#include "xregex.h"

/* Each sed command turns into one of these structures. */
typedef struct sed_cmd_s {
    /* Ordered by alignment requirements: currently 36 bytes on x86 */

    /* address storage */
    regex_t *beg_match; /* sed -e '/match/cmd' */
    regex_t *end_match; /* sed -e '/match/,/end_match/cmd' */
    regex_t *sub_match; /* For 's/sub_match/string/' */
    int beg_line;       /* 'sed 1p'   0 == apply commands to all lines */
    int end_line;       /* 'sed 1,3p' 0 == one line only. -1 = last line ($) */

    FILE *file;         /* File (sw) command writes to, -1 for none. */
    char *string;       /* Data string for (saicytb) commands. */

    unsigned short which_match;     /* (s) Which match to replace (0 for all) */

    /* Bitfields (gcc won't group them if we don't) */
    unsigned int invert:1;          /* the '!' after the address */
    unsigned int in_match:1;        /* Next line also included in match? */
    unsigned int no_newline:1;      /* Last line written by (sw) had no '\n' */
    unsigned int sub_p:1;           /* (s) print option */

    /* GENERAL FIELDS */
    char cmd;               /* The command char: abcdDgGhHilnNpPqrstwxy:={} */
    struct sed_cmd_s *next; /* Next command (linked list, NULL terminated) */
} sed_cmd_t;

static const char bad_format_in_subst[] =
    "bad format in substitution expression";
static const char *const semicolon_whitespace = "; \n\r\t\v";

struct sed_globals
{
    /* options */
    int be_quiet, in_place, regex_type;
    FILE *nonstdout;
    char *outname, *hold_space;

    /* List of input files */
    int input_file_count,current_input_file;
    FILE **input_file_list;

    regmatch_t regmatch[10];
    regex_t *previous_regex_ptr;
    
    /* linked list of sed commands */
    sed_cmd_t sed_cmd_head, *sed_cmd_tail;

    /* Linked list of append lines */
    llist_t *append_head;

    char *add_cmd_line;

    struct pipeline {
        char *buf;  /* Space to hold string */
        int idx;    /* Space used */
        int len;    /* Space allocated */
    } pipeline;
} bbg;


void sed_free_and_close_stuff(void);
#if ENABLE_FEATURE_CLEAN_UP
void sed_free_and_close_stuff(void)
{
    sed_cmd_t *sed_cmd = bbg.sed_cmd_head.next;

    llist_free(bbg.append_head, free);

    while (sed_cmd) {
        sed_cmd_t *sed_cmd_next = sed_cmd->next;

        if(sed_cmd->file)
            bb_xprint_and_close_file(sed_cmd->file);

        if (sed_cmd->beg_match) {
            regfree(sed_cmd->beg_match);
            free(sed_cmd->beg_match);
        }
        if (sed_cmd->end_match) {
            regfree(sed_cmd->end_match);
            free(sed_cmd->end_match);
        }
        if (sed_cmd->sub_match) {
            regfree(sed_cmd->sub_match);
            free(sed_cmd->sub_match);
        }
        free(sed_cmd->string);
        free(sed_cmd);
        sed_cmd = sed_cmd_next;
    }

    if(bbg.hold_space) free(bbg.hold_space);

    while(bbg.current_input_file<bbg.input_file_count)
        fclose(bbg.input_file_list[bbg.current_input_file++]);
}
#endif

/* If something bad happens during -i operation, delete temp file */

static void cleanup_outname(void)
{
  if(bbg.outname) unlink(bbg.outname);
}

/* strdup, replacing "\n" with '\n', and "\delimiter" with 'delimiter' */

static void parse_escapes(char *dest, const char *string, int len, char from, char to)
{
    int i=0;

    while(i<len) {
        if(string[i] == '\\') {
            if(!to || string[i+1] == from) {
                *(dest++) = to ? to : string[i+1];
                i+=2;
                continue;
            } else *(dest++)=string[i++];
        }
        *(dest++) = string[i++];
    }
    *dest=0;
}

static char *copy_parsing_escapes(const char *string, int len)
{
    char *dest=xmalloc(len+1);

    parse_escapes(dest,string,len,'n','\n');
    return dest;
}


/*
 * index_of_next_unescaped_regexp_delim - walks left to right through a string
 * beginning at a specified index and returns the index of the next regular
 * expression delimiter (typically a forward * slash ('/')) not preceded by
 * a backslash ('\').
 */
static int index_of_next_unescaped_regexp_delim(const char delimiter,
    const char *str)
{
    int bracket = -1;
    int escaped = 0;
    int idx = 0;
    char ch;

    for (; (ch = str[idx]); idx++) {
        if (bracket != -1) {
            if (ch == ']' && !(bracket == idx - 1 || (bracket == idx - 2
                    && str[idx - 1] == '^')))
                bracket = -1;
        } else if (escaped)
            escaped = 0;
        else if (ch == '\\')
            escaped = 1;
        else if (ch == '[')
            bracket = idx;
        else if (ch == delimiter)
            return idx;
    }

    /* if we make it to here, we've hit the end of the string */
    return -1;
}

/*
 *  Returns the index of the third delimiter
 */
static int parse_regex_delim(const char *cmdstr, char **match, char **replace)
{
    const char *cmdstr_ptr = cmdstr;
    char delimiter;
    int idx = 0;

    /* verify that the 's' or 'y' is followed by something.  That something
     * (typically a 'slash') is now our regexp delimiter... */
    if (*cmdstr == '\0') bb_error_msg_and_die(bad_format_in_subst);
    delimiter = *(cmdstr_ptr++);

    /* save the match string */
    idx = index_of_next_unescaped_regexp_delim(delimiter, cmdstr_ptr);
    if (idx == -1) {
        bb_error_msg_and_die(bad_format_in_subst);
    }
    *match = copy_parsing_escapes(cmdstr_ptr, idx);

    /* save the replacement string */
    cmdstr_ptr += idx + 1;
    idx = index_of_next_unescaped_regexp_delim(delimiter, cmdstr_ptr);
    if (idx == -1) {
        bb_error_msg_and_die(bad_format_in_subst);
    }
    *replace = copy_parsing_escapes(cmdstr_ptr, idx);

    return ((cmdstr_ptr - cmdstr) + idx);
}

/*
 * returns the index in the string just past where the address ends.
 */
static int get_address(char *my_str, int *linenum, regex_t ** regex)
{
    char *pos = my_str;

    if (isdigit(*my_str)) {
        *linenum = strtol(my_str, &pos, 10);
        /* endstr shouldnt ever equal NULL */
    } else if (*my_str == '$') {
        *linenum = -1;
        pos++;
    } else if (*my_str == '/' || *my_str == '\\') {
        int next;
        char delimiter;
        char *temp;

        if (*my_str == '\\') delimiter = *(++pos);
        else delimiter = '/';
        next = index_of_next_unescaped_regexp_delim(delimiter, ++pos);
        if (next == -1)
            bb_error_msg_and_die("unterminated match expression");

        temp=copy_parsing_escapes(pos,next);
        *regex = (regex_t *) xmalloc(sizeof(regex_t));
        xregcomp(*regex, temp, bbg.regex_type|REG_NEWLINE);
        free(temp);
        /* Move position to next character after last delimiter */
        pos+=(next+1);
    }
    return pos - my_str;
}

/* Grab a filename.  Whitespace at start is skipped, then goes to EOL. */
static int parse_file_cmd(sed_cmd_t *sed_cmd, const char *filecmdstr, char **retval)
{
    int start = 0, idx, hack=0;

    /* Skip whitespace, then grab filename to end of line */
    while (isspace(filecmdstr[start])) start++;
    idx=start;
    while(filecmdstr[idx] && filecmdstr[idx]!='\n') idx++;
    /* If lines glued together, put backslash back. */
    if(filecmdstr[idx]=='\n') hack=1;
    if(idx==start) bb_error_msg_and_die("Empty filename");
    *retval = bb_xstrndup(filecmdstr+start, idx-start+hack+1);
    if(hack) *(idx+*retval)='\\';

    return idx;
}

static int parse_subst_cmd(sed_cmd_t *const sed_cmd, char *substr)
{
    int cflags = bbg.regex_type;
    char *match;
    int idx = 0;

    /*
     * A substitution command should look something like this:
     *    s/match/replace/ #gIpw
     *    ||     |        |||
     *    mandatory       optional
     */
    idx = parse_regex_delim(substr, &match, &sed_cmd->string);

    /* determine the number of back references in the match string */
    /* Note: we compute this here rather than in the do_subst_command()
     * function to save processor time, at the expense of a little more memory
     * (4 bits) per sed_cmd */

    /* process the flags */

    sed_cmd->which_match=1;
    while (substr[++idx]) {
        /* Parse match number */
        if(isdigit(substr[idx])) {
            if(match[0]!='^') {
                /* Match 0 treated as all, multiple matches we take the last one. */
                char *pos=substr+idx;
                sed_cmd->which_match=(unsigned short)strtol(substr+idx,&pos,10);
                idx=pos-substr;
            }
            continue;
        }
        /* Skip spaces */
        if(isspace(substr[idx])) continue;

        switch (substr[idx]) {
            /* Replace all occurrences */
            case 'g':
                if (match[0] != '^') sed_cmd->which_match = 0;
                break;
            /* Print pattern space */
            case 'p':
                sed_cmd->sub_p = 1;
                break;
            /* Write to file */
            case 'w':
            {
                char *temp;
                idx+=parse_file_cmd(sed_cmd,substr+idx,&temp);

                break;
            }
            /* Ignore case (gnu exension) */
            case 'I':
                cflags |= REG_ICASE;
                break;
            /* Comment */
            case '#':
                while(substr[++idx]);
                /* Fall through */
            /* End of command */
            case ';':
            case '}':
                goto out;
            default:
                bb_error_msg_and_die("bad option in substitution expression");
        }
    }
out:
    /* compile the match string into a regex */
    if (*match != '\0') {
        /* If match is empty, we use last regex used at runtime */
        sed_cmd->sub_match = (regex_t *) xmalloc(sizeof(regex_t));
        xregcomp(sed_cmd->sub_match, match, cflags);
    }
    free(match);

    return idx;
}

/*
 *  Process the commands arguments
 */
static char *parse_cmd_args(sed_cmd_t *sed_cmd, char *cmdstr)
{
    /* handle (s)ubstitution command */
    if (sed_cmd->cmd == 's') cmdstr += parse_subst_cmd(sed_cmd, cmdstr);
    /* handle edit cmds: (a)ppend, (i)nsert, and (c)hange */
    else if (strchr("aic", sed_cmd->cmd)) {
        if ((sed_cmd->end_line || sed_cmd->end_match) && sed_cmd->cmd != 'c')
            bb_error_msg_and_die
                ("only a beginning address can be specified for edit commands");
        for(;;) {
            if(*cmdstr=='\n' || *cmdstr=='\\') {
                cmdstr++;
                break;
            } else if(isspace(*cmdstr)) cmdstr++;
            else break;
        }
        sed_cmd->string = bb_xstrdup(cmdstr);
        parse_escapes(sed_cmd->string,sed_cmd->string,strlen(cmdstr),0,0);
        cmdstr += strlen(cmdstr);
    /* handle file cmds: (r)ead */
    } else if(strchr("rw", sed_cmd->cmd)) {
        if (sed_cmd->end_line || sed_cmd->end_match)
            bb_error_msg_and_die("Command only uses one address");
        cmdstr += parse_file_cmd(sed_cmd, cmdstr, &sed_cmd->string);
        if(sed_cmd->cmd=='w')
            sed_cmd->file=bb_xfopen(sed_cmd->string,"w");
    /* handle branch commands */
    } else if (strchr(":btT", sed_cmd->cmd)) {
        int length;

        while(isspace(*cmdstr)) cmdstr++;
        length = strcspn(cmdstr, semicolon_whitespace);
        if (length) {
            sed_cmd->string = bb_xstrndup(cmdstr, length);
            cmdstr += length;
        }
    }
    /* translation command */
    else if (sed_cmd->cmd == 'y') {
        char *match, *replace;
        int i=cmdstr[0];

        cmdstr+=parse_regex_delim(cmdstr, &match, &replace)+1;
        /* \n already parsed, but \delimiter needs unescaping. */
        parse_escapes(match,match,strlen(match),i,i);
        parse_escapes(replace,replace,strlen(replace),i,i);

        sed_cmd->string = xzalloc((strlen(match) + 1) * 2);
        for (i = 0; match[i] && replace[i]; i++) {
            sed_cmd->string[i * 2] = match[i];
            sed_cmd->string[(i * 2) + 1] = replace[i];
        }
        free(match);
        free(replace);
    }
    /* if it wasnt a single-letter command that takes no arguments
     * then it must be an invalid command.
     */
    else if (strchr("dDgGhHlnNpPqx={}", sed_cmd->cmd) == 0) {
        bb_error_msg_and_die("Unsupported command %c", sed_cmd->cmd);
    }

    /* give back whatever's left over */
    return (cmdstr);
}


/* Parse address+command sets, skipping comment lines. */

static void add_cmd(char *cmdstr)
{
    sed_cmd_t *sed_cmd;
    int temp;

    /* Append this line to any unfinished line from last time. */
    if (bbg.add_cmd_line) {
        cmdstr = bb_xasprintf("%s\n%s", bbg.add_cmd_line, cmdstr);
        free(bbg.add_cmd_line);
        bbg.add_cmd_line = cmdstr;
    }

    /* If this line ends with backslash, request next line. */
    temp=strlen(cmdstr);
    if(temp && cmdstr[temp-1]=='\\') {
        if (!bbg.add_cmd_line) bbg.add_cmd_line = bb_xstrdup(cmdstr);
        bbg.add_cmd_line[temp-1] = 0;
        return;
    }

    /* Loop parsing all commands in this line. */
    while(*cmdstr) {
        /* Skip leading whitespace and semicolons */
        cmdstr += strspn(cmdstr, semicolon_whitespace);

        /* If no more commands, exit. */
        if(!*cmdstr) break;

        /* if this is a comment, jump past it and keep going */
        if (*cmdstr == '#') {
            /* "#n" is the same as using -n on the command line */
            if (cmdstr[1] == 'n') bbg.be_quiet++;
            if(!(cmdstr=strpbrk(cmdstr, "\n\r"))) break;
            continue;
        }

        /* parse the command
         * format is: [addr][,addr][!]cmd
         *            |----||-----||-|
         *            part1 part2  part3
         */

        sed_cmd = xzalloc(sizeof(sed_cmd_t));

        /* first part (if present) is an address: either a '$', a number or a /regex/ */
        cmdstr += get_address(cmdstr, &sed_cmd->beg_line, &sed_cmd->beg_match);

        /* second part (if present) will begin with a comma */
        if (*cmdstr == ',') {
            int idx;

            cmdstr++;
            idx = get_address(cmdstr, &sed_cmd->end_line, &sed_cmd->end_match);
            if (!idx) bb_error_msg_and_die("no address after comma\n");
            cmdstr += idx;
        }

        /* skip whitespace before the command */
        while (isspace(*cmdstr)) cmdstr++;

        /* Check for inversion flag */
        if (*cmdstr == '!') {
            sed_cmd->invert = 1;
            cmdstr++;

            /* skip whitespace before the command */
            while (isspace(*cmdstr)) cmdstr++;
        }

        /* last part (mandatory) will be a command */
        if (!*cmdstr) bb_error_msg_and_die("missing command");
        sed_cmd->cmd = *(cmdstr++);
        cmdstr = parse_cmd_args(sed_cmd, cmdstr);

        /* Add the command to the command array */
        bbg.sed_cmd_tail->next = sed_cmd;
        bbg.sed_cmd_tail = bbg.sed_cmd_tail->next;
    }

    /* If we glued multiple lines together, free the memory. */
    free(bbg.add_cmd_line);
    bbg.add_cmd_line = NULL;
}

/* Append to a string, reallocating memory as necessary. */

#define PIPE_GROW 64

static void pipe_putc(char c)
{
    if(bbg.pipeline.idx==bbg.pipeline.len) {
        bbg.pipeline.buf = xrealloc(bbg.pipeline.buf,
                                bbg.pipeline.len + PIPE_GROW);
        bbg.pipeline.len+=PIPE_GROW;
    }
    bbg.pipeline.buf[bbg.pipeline.idx++] = c;
}

static void do_subst_w_backrefs(const char *line, const char *replace)
{
    int i,j;

    /* go through the replacement string */
    for (i = 0; replace[i]; i++) {
        /* if we find a backreference (\1, \2, etc.) print the backref'ed * text */
        if (replace[i] == '\\' && replace[i+1]>='0' && replace[i+1]<='9') {
            int backref=replace[++i]-'0';

            /* print out the text held in bbg.regmatch[backref] */
            if(bbg.regmatch[backref].rm_so != -1)
                for (j = bbg.regmatch[backref].rm_so;
                    j < bbg.regmatch[backref].rm_eo; j++) pipe_putc(line[j]);
        }

        /* if we find a backslash escaped character, print the character */
        else if (replace[i] == '\\') pipe_putc(replace[++i]);

        /* if we find an unescaped '&' print out the whole matched text. */
        else if (replace[i] == '&')
            for (j = bbg.regmatch[0].rm_so; j < bbg.regmatch[0].rm_eo; j++)
                pipe_putc(line[j]);
        /* Otherwise just output the character. */
        else pipe_putc(replace[i]);
    }
}

static int do_subst_command(sed_cmd_t *sed_cmd, char **line)
{
    char *oldline = *line;
    int altered = 0;
    int match_count=0;
    regex_t *current_regex;

    /* Handle empty regex. */
    if (sed_cmd->sub_match == NULL) {
        current_regex = bbg.previous_regex_ptr;
        if(!current_regex)
            bb_error_msg_and_die("No previous regexp.");
    } else bbg.previous_regex_ptr = current_regex = sed_cmd->sub_match;

    /* Find the first match */
    if(REG_NOMATCH==regexec(current_regex, oldline, 10, bbg.regmatch, 0))
        return 0;

    /* Initialize temporary output buffer. */
    bbg.pipeline.buf=xmalloc(PIPE_GROW);
    bbg.pipeline.len=PIPE_GROW;
    bbg.pipeline.idx=0;

    /* Now loop through, substituting for matches */
    do {
        int i;

        /* Work around bug in glibc regexec, demonstrated by:
           echo " a.b" | busybox sed 's [^ .]* x g'
           The match_count check is so not to break
           echo "hi" | busybox sed 's/^/!/g' */
        if(!bbg.regmatch[0].rm_so && !bbg.regmatch[0].rm_eo && match_count) {
            pipe_putc(*(oldline++));
            continue;
        }

        match_count++;

        /* If we aren't interested in this match, output old line to
           end of match and continue */
        if(sed_cmd->which_match && sed_cmd->which_match!=match_count) {
            for(i=0;i<bbg.regmatch[0].rm_eo;i++)
                pipe_putc(oldline[i]);
            continue;
        }

        /* print everything before the match */
        for (i = 0; i < bbg.regmatch[0].rm_so; i++) pipe_putc(oldline[i]);

        /* then print the substitution string */
        do_subst_w_backrefs(oldline, sed_cmd->string);

        /* advance past the match */
        oldline += bbg.regmatch[0].rm_eo;
        /* flag that something has changed */
        altered++;

        /* if we're not doing this globally, get out now */
        if (sed_cmd->which_match) break;
    } while (*oldline && (regexec(current_regex, oldline, 10, bbg.regmatch, 0) != REG_NOMATCH));

    /* Copy rest of string into output pipeline */

    while(*oldline) pipe_putc(*(oldline++));
    pipe_putc(0);

    free(*line);
    *line = bbg.pipeline.buf;
    return altered;
}

/* Set command pointer to point to this label.  (Does not handle null label.) */
static sed_cmd_t *branch_to(const char *label)
{
    sed_cmd_t *sed_cmd;

    for (sed_cmd = bbg.sed_cmd_head.next; sed_cmd; sed_cmd = sed_cmd->next) {
        if ((sed_cmd->cmd == ':') && (sed_cmd->string) && (strcmp(sed_cmd->string, label) == 0)) {
            return (sed_cmd);
        }
    }
    bb_error_msg_and_die("Can't find label for jump to `%s'", label);
}

static void append(char *s)
{
    llist_add_to_end(&bbg.append_head, bb_xstrdup(s));
}

static void flush_append(void)
{
    char *data;

    /* Output appended lines. */
    while((data = (char *)llist_pop(&bbg.append_head))) {
        fprintf(bbg.nonstdout,"%s\n",data);
        free(data);
    }
}

static void add_input_file(FILE *file)
{
    bbg.input_file_list=xrealloc(bbg.input_file_list,
            (bbg.input_file_count + 1) * sizeof(FILE *));
    bbg.input_file_list[bbg.input_file_count++] = file;
}

/* Get next line of input from bbg.input_file_list, flushing append buffer and
 * noting if we ran out of files without a newline on the last line we read.
 */
static char *get_next_line(int *no_newline)
{
    char *temp=NULL;
    int len;

    flush_append();
    while (bbg.current_input_file<bbg.input_file_count) {
        temp = bb_get_chunk_from_file(bbg.input_file_list[bbg.current_input_file],&len);
        if (temp) {
            *no_newline = !(len && temp[len-1]=='\n');
            if (!*no_newline) temp[len-1] = 0;
            break;
        // Close this file and advance to next one
        } else fclose(bbg.input_file_list[bbg.current_input_file++]);
    }

    return temp;
}

/* Output line of text.  missing_newline means the last line output did not
   end with a newline.  no_newline means this line does not end with a
   newline. */

static int puts_maybe_newline(char *s, FILE *file, int missing_newline, int no_newline)
{
    if(missing_newline) fputc('\n',file);
    fputs(s,file);
    if(!no_newline) fputc('\n',file);

    if(ferror(file)) {
        bb_default_error_retval = 4;  /* It's what gnu sed exits with... */
        bb_error_msg_and_die(bb_msg_write_error);
    }

    return no_newline;
}

#define sed_puts(s,n) missing_newline=puts_maybe_newline(s,bbg.nonstdout,missing_newline,n)

/* Process all the lines in all the files */

static void process_files(void)
{
    char *pattern_space, *next_line;
    int linenum = 0, missing_newline=0;
    int no_newline,next_no_newline=0;

    /* Prime the pump */
    next_line = get_next_line(&next_no_newline);

    /* go through every line in each file */
    for(;;) {
        sed_cmd_t *sed_cmd;
        int substituted=0;

        /* Advance to next line.  Stop if out of lines. */
        if(!(pattern_space=next_line)) break;
        no_newline=next_no_newline;

        /* Read one line in advance so we can act on the last line,
         * the '$' address */
        next_line = get_next_line(&next_no_newline);
        linenum++;
restart:
        /* for every line, go through all the commands */
        for (sed_cmd = bbg.sed_cmd_head.next; sed_cmd; sed_cmd = sed_cmd->next)
        {
            int old_matched, matched;

            old_matched = sed_cmd->in_match;

            /* Determine if this command matches this line: */

            /* Are we continuing a previous multi-line match? */

            sed_cmd->in_match = sed_cmd->in_match

            /* Or is no range necessary? */
                || (!sed_cmd->beg_line && !sed_cmd->end_line
                    && !sed_cmd->beg_match && !sed_cmd->end_match)

            /* Or did we match the start of a numerical range? */
                || (sed_cmd->beg_line > 0 && (sed_cmd->beg_line == linenum))

            /* Or does this line match our begin address regex? */
                    || (sed_cmd->beg_match &&
                    !regexec(sed_cmd->beg_match, pattern_space, 0, NULL, 0))

            /* Or did we match last line of input? */
                || (sed_cmd->beg_line == -1 && next_line == NULL);

            /* Snapshot the value */

            matched = sed_cmd->in_match;

            /* Is this line the end of the current match? */

            if(matched) {
                sed_cmd->in_match = !(
                    /* has the ending line come, or is this a single address command? */
                    (sed_cmd->end_line ?
                        sed_cmd->end_line==-1 ?
                            !next_line
                            : sed_cmd->end_line<=linenum
                        : !sed_cmd->end_match)
                    /* or does this line matches our last address regex */
                    || (sed_cmd->end_match && old_matched && (regexec(sed_cmd->end_match, pattern_space, 0, NULL, 0) == 0))
                );
            }

            /* Skip blocks of commands we didn't match. */
            if (sed_cmd->cmd == '{') {
                if(sed_cmd->invert ? matched : !matched)
                    while(sed_cmd && sed_cmd->cmd!='}') sed_cmd=sed_cmd->next;
                if(!sed_cmd) bb_error_msg_and_die("Unterminated {");
                continue;
            }

            /* Okay, so did this line match? */
            if (sed_cmd->invert ? !matched : matched) {
                /* Update last used regex in case a blank substitute BRE is found */
                if (sed_cmd->beg_match) {
                    bbg.previous_regex_ptr = sed_cmd->beg_match;
                }

                /* actual sedding */
                switch (sed_cmd->cmd) {

                    /* Print line number */
                    case '=':
                        fprintf(bbg.nonstdout,"%d\n", linenum);
                        break;

                    /* Write the current pattern space up to the first newline */
                    case 'P':
                    {
                        char *tmp = strchr(pattern_space, '\n');

                        if (tmp) {
                            *tmp = '\0';
                            sed_puts(pattern_space,1);
                            *tmp = '\n';
                            break;
                        }
                        /* Fall Through */
                    }

                    /* Write the current pattern space to output */
                    case 'p':
                        sed_puts(pattern_space,no_newline);
                        break;
                    /* Delete up through first newline */
                    case 'D':
                    {
                        char *tmp = strchr(pattern_space,'\n');

                        if(tmp) {
                            tmp=bb_xstrdup(tmp+1);
                            free(pattern_space);
                            pattern_space=tmp;
                            goto restart;
                        }
                    }
                    /* discard this line. */
                    case 'd':
                        goto discard_line;

                    /* Substitute with regex */
                    case 's':
                        if(do_subst_command(sed_cmd, &pattern_space)) {
                            substituted|=1;

                            /* handle p option */
                            if(sed_cmd->sub_p)
                                sed_puts(pattern_space,no_newline);
                            /* handle w option */
                            if(sed_cmd->file)
                                sed_cmd->no_newline=puts_maybe_newline(pattern_space, sed_cmd->file, sed_cmd->no_newline, no_newline);

                        }
                        break;

                    /* Append line to linked list to be printed later */
                    case 'a':
                    {
                        append(sed_cmd->string);
                        break;
                    }

                    /* Insert text before this line */
                    case 'i':
                        sed_puts(sed_cmd->string,1);
                        break;

                    /* Cut and paste text (replace) */
                    case 'c':
                        /* Only triggers on last line of a matching range. */
                        if (!sed_cmd->in_match) sed_puts(sed_cmd->string,0);
                        goto discard_line;

                    /* Read file, append contents to output */
                    case 'r':
                    {
                        FILE *rfile;

                        rfile = fopen(sed_cmd->string, "r");
                        if (rfile) {
                            char *line;

                            while ((line = bb_get_chomped_line_from_file(rfile))
                                    != NULL)
                                append(line);
                            bb_xprint_and_close_file(rfile);
                        }

                        break;
                    }

                    /* Write pattern space to file. */
                    case 'w':
                        sed_cmd->no_newline=puts_maybe_newline(pattern_space,sed_cmd->file, sed_cmd->no_newline,no_newline);
                        break;

                    /* Read next line from input */
                    case 'n':
                        if (!bbg.be_quiet)
                            sed_puts(pattern_space,no_newline);
                        if (next_line) {
                            free(pattern_space);
                            pattern_space = next_line;
                            no_newline=next_no_newline;
                            next_line = get_next_line(&next_no_newline);
                            linenum++;
                            break;
                        }
                        /* fall through */

                    /* Quit.  End of script, end of input. */
                    case 'q':
                        /* Exit the outer while loop */
                        free(next_line);
                        next_line = NULL;
                        goto discard_commands;

                    /* Append the next line to the current line */
                    case 'N':
                    {
                        /* If no next line, jump to end of script and exit. */
                        if (next_line == NULL) {
                            /* Jump to end of script and exit */
                            free(next_line);
                            next_line = NULL;
                            goto discard_line;
                        /* append next_line, read new next_line. */
                        } else {
                            int len=strlen(pattern_space);

                            pattern_space = realloc(pattern_space, len + strlen(next_line) + 2);
                            pattern_space[len]='\n';
                            strcpy(pattern_space+len+1, next_line);
                            no_newline=next_no_newline;
                            next_line = get_next_line(&next_no_newline);
                            linenum++;
                        }
                        break;
                    }

                    /* Test/branch if substitution occurred */
                    case 't':
                        if(!substituted) break;
                        substituted=0;
                        /* Fall through */
                    /* Test/branch if substitution didn't occur */
                    case 'T':
                        if (substituted) break;
                        /* Fall through */
                    /* Branch to label */
                    case 'b':
                        if (!sed_cmd->string) goto discard_commands;
                        else sed_cmd = branch_to(sed_cmd->string);
                        break;
                    /* Transliterate characters */
                    case 'y':
                    {
                        int i;

                        for (i = 0; pattern_space[i]; i++) {
                            int j;

                            for (j = 0; sed_cmd->string[j]; j += 2) {
                                if (pattern_space[i] == sed_cmd->string[j]) {
                                    pattern_space[i] = sed_cmd->string[j + 1];
                                    break;
                                }
                            }
                        }

                        break;
                    }
                    case 'g':   /* Replace pattern space with hold space */
                        free(pattern_space);
                        pattern_space = bb_xstrdup(bbg.hold_space ? bbg.hold_space : "");
                        break;
                    case 'G':   /* Append newline and hold space to pattern space */
                    {
                        int pattern_space_size = 2;
                        int hold_space_size = 0;

                        if (pattern_space)
                            pattern_space_size += strlen(pattern_space);
                        if (bbg.hold_space)
                            hold_space_size = strlen(bbg.hold_space);
                        pattern_space = xrealloc(pattern_space,
                                pattern_space_size + hold_space_size);
                        if (pattern_space_size == 2) pattern_space[0]=0;
                        strcat(pattern_space, "\n");
                        if (bbg.hold_space)
                            strcat(pattern_space, bbg.hold_space);
                        no_newline=0;

                        break;
                    }
                    case 'h':   /* Replace hold space with pattern space */
                        free(bbg.hold_space);
                        bbg.hold_space = bb_xstrdup(pattern_space);
                        break;
                    case 'H':   /* Append newline and pattern space to hold space */
                    {
                        int hold_space_size = 2;
                        int pattern_space_size = 0;

                        if (bbg.hold_space)
                            hold_space_size += strlen(bbg.hold_space);
                        if (pattern_space)
                            pattern_space_size = strlen(pattern_space);
                        bbg.hold_space = xrealloc(bbg.hold_space,
                                            hold_space_size + pattern_space_size);

                        if (hold_space_size == 2) *bbg.hold_space=0;
                        strcat(bbg.hold_space, "\n");
                        if (pattern_space) strcat(bbg.hold_space, pattern_space);

                        break;
                    }
                    case 'x': /* Exchange hold and pattern space */
                    {
                        char *tmp = pattern_space;
                        pattern_space = bbg.hold_space ? : xzalloc(1);
                        no_newline=0;
                        bbg.hold_space = tmp;
                        break;
                    }
                }
            }
        }

        /*
         * exit point from sedding...
         */
discard_commands:
        /* we will print the line unless we were told to be quiet ('-n')
           or if the line was suppressed (ala 'd'elete) */
        if (!bbg.be_quiet) sed_puts(pattern_space,no_newline);

        /* Delete and such jump here. */
discard_line:
        flush_append();
        free(pattern_space);
    }
}

/* It is possible to have a command line argument with embedded
   newlines.  This counts as multiple command lines. */

static void add_cmd_block(char *cmdstr)
{
    int go=1;
    char *temp=bb_xstrdup(cmdstr),*temp2=temp;

    while(go) {
        int len=strcspn(temp2,"\n");
        if(!temp2[len]) go=0;
        else temp2[len]=0;
        add_cmd(temp2);
        temp2+=len+1;
    }
    free(temp);
}

int sed_main(int argc, char **argv)
{
    int status = EXIT_SUCCESS, opt, getpat = 1;

    bbg.sed_cmd_tail=&bbg.sed_cmd_head;

    /* destroy command strings on exit */
    if (ENABLE_FEATURE_CLEAN_UP) atexit(sed_free_and_close_stuff);

    /* Lie to autoconf when it starts asking stupid questions. */
    if(argc==2 && !strcmp(argv[1],"--version")) {
        printf("This is not GNU sed version 4.0\n");
        exit(0);
    }

    /* do normal option parsing */
    while ((opt = getopt(argc, argv, "irne:f:")) > 0) {
        switch (opt) {
        case 'i':
            bbg.in_place++;
            atexit(cleanup_outname);
            break;
        case 'r':
            bbg.regex_type|=REG_EXTENDED;
            break;
        case 'n':
            bbg.be_quiet++;
            break;
        case 'e':
            add_cmd_block(optarg);
            getpat=0;
            break;
        case 'f':
        {
            FILE *cmdfile;
            char *line;

            cmdfile = bb_xfopen(optarg, "r");

            while ((line = bb_get_chomped_line_from_file(cmdfile)) != NULL) {
                add_cmd(line);
                getpat=0;
                free(line);
            }
            bb_xprint_and_close_file(cmdfile);

            break;
        }
        default:
            bb_show_usage();
        }
    }

    /* if we didn't get a pattern from -e or -f, use argv[optind] */
    if(getpat) {
        if (argv[optind] == NULL)
            bb_show_usage();
        else
            add_cmd_block(argv[optind++]);
    }
    /* Flush any unfinished commands. */
    add_cmd("");

    /* By default, we write to stdout */
    bbg.nonstdout=stdout;

    /* argv[(optind)..(argc-1)] should be names of file to process. If no
     * files were specified or '-' was specified, take input from stdin.
     * Otherwise, we process all the files specified. */
    if (argv[optind] == NULL) {
        if(bbg.in_place) bb_error_msg_and_die(bb_msg_requires_arg, "-i");
        add_input_file(stdin);
        process_files();
    } else {
        int i;
        FILE *file;

        for (i = optind; i < argc; i++) {
            if(!strcmp(argv[i], "-") && !bbg.in_place) {
                add_input_file(stdin);
                process_files();
            } else {
                file = bb_wfopen(argv[i], "r");
                if (file) {
                    if(bbg.in_place) {
                        struct stat statbuf;
                        int nonstdoutfd;

                        bbg.outname=bb_xstrndup(argv[i],strlen(argv[i])+6);
                        strcat(bbg.outname,"XXXXXX");
                        if(-1==(nonstdoutfd=mkstemp(bbg.outname)))
                            bb_error_msg_and_die("no temp file");
                        bbg.nonstdout=fdopen(nonstdoutfd,"w");

                        /* Set permissions of output file */

                        fstat(fileno(file),&statbuf);
                        fchmod(nonstdoutfd,statbuf.st_mode);
                        add_input_file(file);
                        process_files();
                        fclose(bbg.nonstdout);

                        bbg.nonstdout=stdout;
                        unlink(argv[i]);
                        rename(bbg.outname,argv[i]);
                        free(bbg.outname);
                        bbg.outname=0;
                    } else add_input_file(file);
                } else {
                    status = EXIT_FAILURE;
                }
            }
        }
        if(bbg.input_file_count>bbg.current_input_file) process_files();
    }

    return status;
}