source: MondoRescue/branches/3.2/mindi-busybox/miscutils/crond.c@ 3262

/* vi: set sw=4 ts=4: */
/*
 * crond -d[#] -c <crondir> -f -b
 *
 * run as root, but NOT setuid root
 *
 * Copyright 1994 Matthew Dillon (dillon@apollo.west.oic.com)
 * (version 2.3.2)
 * Vladimir Oleynik <dzo@simtreas.ru> (C) 2002
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */

//usage:#define crond_trivial_usage
//usage:       "-fbS -l N " IF_FEATURE_CROND_D("-d N ") "-L LOGFILE -c DIR"
//usage:#define crond_full_usage "\n\n"
//usage:       "    -f  Foreground"
//usage:     "\n    -b  Background (default)"
//usage:     "\n    -S  Log to syslog (default)"
//usage:     "\n    -l  Set log level. 0 is the most verbose, default 8"
//usage:    IF_FEATURE_CROND_D(
//usage:     "\n    -d  Set log level, log to stderr"
//usage:    )
//usage:     "\n    -L  Log to file"
//usage:     "\n    -c  Working dir"

#include "libbb.h"
#include <syslog.h>

/* glibc frees previous setenv'ed value when we do next setenv()
 * of the same variable. uclibc does not do this! */
#if (defined(__GLIBC__) && !defined(__UCLIBC__)) /* || OTHER_SAFE_LIBC... */
# define SETENV_LEAKS 0
#else
# define SETENV_LEAKS 1
#endif


#define TMPDIR          CONFIG_FEATURE_CROND_DIR
#define CRONTABS        CONFIG_FEATURE_CROND_DIR "/crontabs"
#ifndef SENDMAIL
# define SENDMAIL       "sendmail"
#endif
#ifndef SENDMAIL_ARGS
# define SENDMAIL_ARGS  "-ti"
#endif
#ifndef CRONUPDATE
# define CRONUPDATE     "cron.update"
#endif
#ifndef MAXLINES
# define MAXLINES       256  /* max lines in non-root crontabs */
#endif


typedef struct CronFile {
    struct CronFile *cf_next;
    struct CronLine *cf_lines;
    char *cf_username;
    smallint cf_wants_starting;     /* bool: one or more jobs ready */
    smallint cf_has_running;        /* bool: one or more jobs running */
    smallint cf_deleted;            /* marked for deletion (but still has running jobs) */
} CronFile;

typedef struct CronLine {
    struct CronLine *cl_next;
    char *cl_cmd;                   /* shell command */
    pid_t cl_pid;                   /* >0:running, <0:needs to be started in this minute, 0:dormant */
#if ENABLE_FEATURE_CROND_CALL_SENDMAIL
    int cl_empty_mail_size;         /* size of mail header only, 0 if no mailfile */
    char *cl_mailto;                /* whom to mail results, may be NULL */
#endif
    /* ordered by size, not in natural order. makes code smaller: */
    char cl_Dow[7];                 /* 0-6, beginning sunday */
    char cl_Mons[12];               /* 0-11 */
    char cl_Hrs[24];                /* 0-23 */
    char cl_Days[32];               /* 1-31 */
    char cl_Mins[60];               /* 0-59 */
} CronLine;


#define DAEMON_UID 0


enum {
    OPT_l = (1 << 0),
    OPT_L = (1 << 1),
    OPT_f = (1 << 2),
    OPT_b = (1 << 3),
    OPT_S = (1 << 4),
    OPT_c = (1 << 5),
    OPT_d = (1 << 6) * ENABLE_FEATURE_CROND_D,
};
#if ENABLE_FEATURE_CROND_D
# define DebugOpt (option_mask32 & OPT_d)
#else
# define DebugOpt 0
#endif


struct globals {
    unsigned log_level; /* = 8; */
    time_t crontab_dir_mtime;
    const char *log_filename;
    const char *crontab_dir_name; /* = CRONTABS; */
    CronFile *cron_files;
#if SETENV_LEAKS
    char *env_var_user;
    char *env_var_home;
#endif
} FIX_ALIASING;
#define G (*(struct globals*)&bb_common_bufsiz1)
#define INIT_G() do { \
    G.log_level = 8; \
    G.crontab_dir_name = CRONTABS; \
} while (0)


/* 0 is the most verbose, default 8 */
#define LVL5  "\x05"
#define LVL7  "\x07"
#define LVL8  "\x08"
#define WARN9 "\x49"
#define DIE9  "\xc9"
/* level >= 20 is "error" */
#define ERR20 "\x14"

static void crondlog(const char *ctl, ...) __attribute__ ((format (printf, 1, 2)));
static void crondlog(const char *ctl, ...)
{
    va_list va;
    int level = (ctl[0] & 0x1f);

    va_start(va, ctl);
    if (level >= (int)G.log_level) {
        /* Debug mode: all to (non-redirected) stderr, */
        /* Syslog mode: all to syslog (logmode = LOGMODE_SYSLOG), */
        if (!DebugOpt && G.log_filename) {
            /* Otherwise (log to file): we reopen log file at every write: */
            int logfd = open_or_warn(G.log_filename, O_WRONLY | O_CREAT | O_APPEND);
            if (logfd >= 0)
                xmove_fd(logfd, STDERR_FILENO);
        }
        /* When we log to syslog, level > 8 is logged at LOG_ERR
         * syslog level, level <= 8 is logged at LOG_INFO. */
        if (level > 8) {
            bb_verror_msg(ctl + 1, va, /* strerr: */ NULL);
        } else {
            char *msg = NULL;
            vasprintf(&msg, ctl + 1, va);
            bb_info_msg("%s: %s", applet_name, msg);
            free(msg);
        }
    }
    va_end(va);
    if (ctl[0] & 0x80)
        exit(20);
}

static const char DowAry[] ALIGN1 =
    "sun""mon""tue""wed""thu""fri""sat"
    /* "Sun""Mon""Tue""Wed""Thu""Fri""Sat" */
;

static const char MonAry[] ALIGN1 =
    "jan""feb""mar""apr""may""jun""jul""aug""sep""oct""nov""dec"
    /* "Jan""Feb""Mar""Apr""May""Jun""Jul""Aug""Sep""Oct""Nov""Dec" */
;

static void ParseField(char *user, char *ary, int modvalue, int off,
                const char *names, char *ptr)
/* 'names' is a pointer to a set of 3-char abbreviations */
{
    char *base = ptr;
    int n1 = -1;
    int n2 = -1;

    // this can't happen due to config_read()
    /*if (base == NULL)
        return;*/

    while (1) {
        int skip = 0;

        /* Handle numeric digit or symbol or '*' */
        if (*ptr == '*') {
            n1 = 0;  /* everything will be filled */
            n2 = modvalue - 1;
            skip = 1;
            ++ptr;
        } else if (isdigit(*ptr)) {
            char *endp;
            if (n1 < 0) {
                n1 = strtol(ptr, &endp, 10) + off;
            } else {
                n2 = strtol(ptr, &endp, 10) + off;
            }
            ptr = endp; /* gcc likes temp var for &endp */
            skip = 1;
        } else if (names) {
            int i;

            for (i = 0; names[i]; i += 3) {
                /* was using strncmp before... */
                if (strncasecmp(ptr, &names[i], 3) == 0) {
                    ptr += 3;
                    if (n1 < 0) {
                        n1 = i / 3;
                    } else {
                        n2 = i / 3;
                    }
                    skip = 1;
                    break;
                }
            }
        }

        /* handle optional range '-' */
        if (skip == 0) {
            goto err;
        }
        if (*ptr == '-' && n2 < 0) {
            ++ptr;
            continue;
        }

        /*
         * collapse single-value ranges, handle skipmark, and fill
         * in the character array appropriately.
         */
        if (n2 < 0) {
            n2 = n1;
        }
        if (*ptr == '/') {
            char *endp;
            skip = strtol(ptr + 1, &endp, 10);
            ptr = endp; /* gcc likes temp var for &endp */
        }

        /*
         * fill array, using a failsafe is the easiest way to prevent
         * an endless loop
         */
        {
            int s0 = 1;
            int failsafe = 1024;

            --n1;
            do {
                n1 = (n1 + 1) % modvalue;

                if (--s0 == 0) {
                    ary[n1 % modvalue] = 1;
                    s0 = skip;
                }
                if (--failsafe == 0) {
                    goto err;
                }
            } while (n1 != n2);
        }
        if (*ptr != ',') {
            break;
        }
        ++ptr;
        n1 = -1;
        n2 = -1;
    }

    if (*ptr) {
 err:
        crondlog(WARN9 "user %s: parse error at %s", user, base);
        return;
    }

    if (DebugOpt && (G.log_level <= 5)) { /* like LVL5 */
        /* can't use crondlog, it inserts '\n' */
        int i;
        for (i = 0; i < modvalue; ++i)
            fprintf(stderr, "%d", (unsigned char)ary[i]);
        bb_putchar_stderr('\n');
    }
}

static void FixDayDow(CronLine *line)
{
    unsigned i;
    int weekUsed = 0;
    int daysUsed = 0;

    for (i = 0; i < ARRAY_SIZE(line->cl_Dow); ++i) {
        if (line->cl_Dow[i] == 0) {
            weekUsed = 1;
            break;
        }
    }
    for (i = 0; i < ARRAY_SIZE(line->cl_Days); ++i) {
        if (line->cl_Days[i] == 0) {
            daysUsed = 1;
            break;
        }
    }
    if (weekUsed != daysUsed) {
        if (weekUsed)
            memset(line->cl_Days, 0, sizeof(line->cl_Days));
        else /* daysUsed */
            memset(line->cl_Dow, 0, sizeof(line->cl_Dow));
    }
}

/*
 * delete_cronfile() - delete user database
 *
 * Note: multiple entries for same user may exist if we were unable to
 * completely delete a database due to running processes.
 */
//FIXME: we will start a new job even if the old job is running
//if crontab was reloaded: crond thinks that "new" job is different from "old"
//even if they are in fact completely the same. Example
//Crontab was:
// 0-59 * * * * job1
// 0-59 * * * * long_running_job2
//User edits crontab to:
// 0-59 * * * * job1_updated
// 0-59 * * * * long_running_job2
//Bug: crond can now start another long_running_job2 even if old one
//is still running.
//OTOH most other versions of cron do not wait for job termination anyway,
//they end up with multiple copies of jobs if they don't terminate soon enough.
static void delete_cronfile(const char *userName)
{
    CronFile **pfile = &G.cron_files;
    CronFile *file;

    while ((file = *pfile) != NULL) {
        if (strcmp(userName, file->cf_username) == 0) {
            CronLine **pline = &file->cf_lines;
            CronLine *line;

            file->cf_has_running = 0;
            file->cf_deleted = 1;

            while ((line = *pline) != NULL) {
                if (line->cl_pid > 0) {
                    file->cf_has_running = 1;
                    pline = &line->cl_next;
                } else {
                    *pline = line->cl_next;
                    free(line->cl_cmd);
                    free(line);
                }
            }
            if (file->cf_has_running == 0) {
                *pfile = file->cf_next;
                free(file->cf_username);
                free(file);
                continue;
            }
        }
        pfile = &file->cf_next;
    }
}

static void load_crontab(const char *fileName)
{
    struct parser_t *parser;
    struct stat sbuf;
    int maxLines;
    char *tokens[6];
#if ENABLE_FEATURE_CROND_CALL_SENDMAIL
    char *mailTo = NULL;
#endif

    delete_cronfile(fileName);

    if (!getpwnam(fileName)) {
        crondlog(LVL7 "ignoring file '%s' (no such user)", fileName);
        return;
    }

    parser = config_open(fileName);
    if (!parser)
        return;

    maxLines = (strcmp(fileName, "root") == 0) ? 65535 : MAXLINES;

    if (fstat(fileno(parser->fp), &sbuf) == 0 && sbuf.st_uid == DAEMON_UID) {
        CronFile *file = xzalloc(sizeof(CronFile));
        CronLine **pline;
        int n;

        file->cf_username = xstrdup(fileName);
        pline = &file->cf_lines;

        while (1) {
            CronLine *line;

            if (!--maxLines)
                break;
            n = config_read(parser, tokens, 6, 1, "# \t", PARSE_NORMAL | PARSE_KEEP_COPY);
            if (!n)
                break;

            if (DebugOpt)
                crondlog(LVL5 "user:%s entry:%s", fileName, parser->data);

            /* check if line is setting MAILTO= */
            if (0 == strncmp(tokens[0], "MAILTO=", 7)) {
#if ENABLE_FEATURE_CROND_CALL_SENDMAIL
                free(mailTo);
                mailTo = (tokens[0][7]) ? xstrdup(&tokens[0][7]) : NULL;
#endif /* otherwise just ignore such lines */
                continue;
            }
            /* check if a minimum of tokens is specified */
            if (n < 6)
                continue;
            *pline = line = xzalloc(sizeof(*line));
            /* parse date ranges */
            ParseField(file->cf_username, line->cl_Mins, 60, 0, NULL, tokens[0]);
            ParseField(file->cf_username, line->cl_Hrs, 24, 0, NULL, tokens[1]);
            ParseField(file->cf_username, line->cl_Days, 32, 0, NULL, tokens[2]);
            ParseField(file->cf_username, line->cl_Mons, 12, -1, MonAry, tokens[3]);
            ParseField(file->cf_username, line->cl_Dow, 7, 0, DowAry, tokens[4]);
            /*
             * fix days and dow - if one is not "*" and the other
             * is "*", the other is set to 0, and vise-versa
             */
            FixDayDow(line);
#if ENABLE_FEATURE_CROND_CALL_SENDMAIL
            /* copy mailto (can be NULL) */
            line->cl_mailto = xstrdup(mailTo);
#endif
            /* copy command */
            line->cl_cmd = xstrdup(tokens[5]);
            if (DebugOpt) {
                crondlog(LVL5 " command:%s", tokens[5]);
            }
            pline = &line->cl_next;
//bb_error_msg("M[%s]F[%s][%s][%s][%s][%s][%s]", mailTo, tokens[0], tokens[1], tokens[2], tokens[3], tokens[4], tokens[5]);
        }
        *pline = NULL;

        file->cf_next = G.cron_files;
        G.cron_files = file;

        if (maxLines == 0) {
            crondlog(WARN9 "user %s: too many lines", fileName);
        }
    }
    config_close(parser);
}

static void process_cron_update_file(void)
{
    FILE *fi;
    char buf[256];

    fi = fopen_for_read(CRONUPDATE);
    if (fi != NULL) {
        unlink(CRONUPDATE);
        while (fgets(buf, sizeof(buf), fi) != NULL) {
            /* use first word only */
            skip_non_whitespace(buf)[0] = '\0';
            load_crontab(buf);
        }
        fclose(fi);
    }
}

static void rescan_crontab_dir(void)
{
    CronFile *file;

    /* Delete all files until we only have ones with running jobs (or none) */
 again:
    for (file = G.cron_files; file; file = file->cf_next) {
        if (!file->cf_deleted) {
            delete_cronfile(file->cf_username);
            goto again;
        }
    }

    /* Remove cron update file */
    unlink(CRONUPDATE);
    /* Re-chdir, in case directory was renamed & deleted */
    if (chdir(G.crontab_dir_name) < 0) {
        crondlog(DIE9 "chdir(%s)", G.crontab_dir_name);
    }

    /* Scan directory and add associated users */
    {
        DIR *dir = opendir(".");
        struct dirent *den;

        if (!dir)
            crondlog(DIE9 "chdir(%s)", "."); /* exits */
        while ((den = readdir(dir)) != NULL) {
            if (strchr(den->d_name, '.') != NULL) {
                continue;
            }
            load_crontab(den->d_name);
        }
        closedir(dir);
    }
}

#if SETENV_LEAKS
/* We set environment *before* vfork (because we want to use vfork),
 * so we cannot use setenv() - repeated calls to setenv() may leak memory!
 * Using putenv(), and freeing memory after unsetenv() won't leak */
static void safe_setenv(char **pvar_val, const char *var, const char *val)
{
    char *var_val = *pvar_val;

    if (var_val) {
        bb_unsetenv_and_free(var_val);
    }
    *pvar_val = xasprintf("%s=%s", var, val);
    putenv(*pvar_val);
}
#endif

static void set_env_vars(struct passwd *pas)
{
#if SETENV_LEAKS
    safe_setenv(&G.env_var_user, "USER", pas->pw_name);
    safe_setenv(&G.env_var_home, "HOME", pas->pw_dir);
    /* if we want to set user's shell instead: */
    /*safe_setenv(G.env_var_shell, "SHELL", pas->pw_shell);*/
#else
    xsetenv("USER", pas->pw_name);
    xsetenv("HOME", pas->pw_dir);
#endif
    /* currently, we use constant one: */
    /*setenv("SHELL", DEFAULT_SHELL, 1); - done earlier */
}

static void change_user(struct passwd *pas)
{
    /* careful: we're after vfork! */
    change_identity(pas); /* - initgroups, setgid, setuid */
    if (chdir(pas->pw_dir) < 0) {
        crondlog(WARN9 "chdir(%s)", pas->pw_dir);
        if (chdir(TMPDIR) < 0) {
            crondlog(DIE9 "chdir(%s)", TMPDIR); /* exits */
        }
    }
}

// TODO: sendmail should be _run-time_ option, not compile-time!
#if ENABLE_FEATURE_CROND_CALL_SENDMAIL

static pid_t
fork_job(const char *user, int mailFd,
        const char *prog,
        const char *shell_cmd /* if NULL, we run sendmail */
) {
    struct passwd *pas;
    pid_t pid;

    /* prepare things before vfork */
    pas = getpwnam(user);
    if (!pas) {
        crondlog(WARN9 "can't get uid for %s", user);
        goto err;
    }
    set_env_vars(pas);

    pid = vfork();
    if (pid == 0) {
        /* CHILD */
        /* initgroups, setgid, setuid, and chdir to home or TMPDIR */
        change_user(pas);
        if (DebugOpt) {
            crondlog(LVL5 "child running %s", prog);
        }
        if (mailFd >= 0) {
            xmove_fd(mailFd, shell_cmd ? 1 : 0);
            dup2(1, 2);
        }
        /* crond 3.0pl1-100 puts tasks in separate process groups */
        bb_setpgrp();
        execlp(prog, prog, (shell_cmd ? "-c" : SENDMAIL_ARGS), shell_cmd, (char *) NULL);
        crondlog(ERR20 "can't execute '%s' for user %s", prog, user);
        if (shell_cmd) {
            fdprintf(1, "Exec failed: %s -c %s\n", prog, shell_cmd);
        }
        _exit(EXIT_SUCCESS);
    }

    if (pid < 0) {
        /* FORK FAILED */
        crondlog(ERR20 "can't vfork");
 err:
        pid = 0;
    } /* else: PARENT, FORK SUCCESS */

    /*
     * Close the mail file descriptor.. we can't just leave it open in
     * a structure, closing it later, because we might run out of descriptors
     */
    if (mailFd >= 0) {
        close(mailFd);
    }
    return pid;
}

static void start_one_job(const char *user, CronLine *line)
{
    char mailFile[128];
    int mailFd = -1;

    line->cl_pid = 0;
    line->cl_empty_mail_size = 0;

    if (line->cl_mailto) {
        /* Open mail file (owner is root so nobody can screw with it) */
        snprintf(mailFile, sizeof(mailFile), "%s/cron.%s.%d", TMPDIR, user, getpid());
        mailFd = open(mailFile, O_CREAT | O_TRUNC | O_WRONLY | O_EXCL | O_APPEND, 0600);

        if (mailFd >= 0) {
            fdprintf(mailFd, "To: %s\nSubject: cron: %s\n\n", line->cl_mailto,
                line->cl_cmd);
            line->cl_empty_mail_size = lseek(mailFd, 0, SEEK_CUR);
        } else {
            crondlog(ERR20 "can't create mail file %s for user %s, "
                    "discarding output", mailFile, user);
        }
    }

    line->cl_pid = fork_job(user, mailFd, DEFAULT_SHELL, line->cl_cmd);
    if (mailFd >= 0) {
        if (line->cl_pid <= 0) {
            unlink(mailFile);
        } else {
            /* rename mail-file based on pid of process */
            char *mailFile2 = xasprintf("%s/cron.%s.%d", TMPDIR, user, (int)line->cl_pid);
            rename(mailFile, mailFile2); // TODO: xrename?
            free(mailFile2);
        }
    }
}

/*
 * process_finished_job - called when job terminates and when mail terminates
 */
static void process_finished_job(const char *user, CronLine *line)
{
    pid_t pid;
    int mailFd;
    char mailFile[128];
    struct stat sbuf;

    pid = line->cl_pid;
    line->cl_pid = 0;
    if (pid <= 0) {
        /* No job */
        return;
    }
    if (line->cl_empty_mail_size <= 0) {
        /* End of job and no mail file, or end of sendmail job */
        return;
    }

    /*
     * End of primary job - check for mail file.
     * If size has changed and the file is still valid, we send it.
     */
    snprintf(mailFile, sizeof(mailFile), "%s/cron.%s.%d", TMPDIR, user, (int)pid);
    mailFd = open(mailFile, O_RDONLY);
    unlink(mailFile);
    if (mailFd < 0) {
        return;
    }

    if (fstat(mailFd, &sbuf) < 0
     || sbuf.st_uid != DAEMON_UID
     || sbuf.st_nlink != 0
     || sbuf.st_size == line->cl_empty_mail_size
     || !S_ISREG(sbuf.st_mode)
    ) {
        close(mailFd);
        return;
    }
    line->cl_empty_mail_size = 0;
    /* if (line->cl_mailto) - always true if cl_empty_mail_size was nonzero */
        line->cl_pid = fork_job(user, mailFd, SENDMAIL, NULL);
}

#else /* !ENABLE_FEATURE_CROND_CALL_SENDMAIL */

static void start_one_job(const char *user, CronLine *line)
{
    struct passwd *pas;
    pid_t pid;

    pas = getpwnam(user);
    if (!pas) {
        crondlog(WARN9 "can't get uid for %s", user);
        goto err;
    }

    /* Prepare things before vfork */
    set_env_vars(pas);

    /* Fork as the user in question and run program */
    pid = vfork();
    if (pid == 0) {
        /* CHILD */
        /* initgroups, setgid, setuid, and chdir to home or TMPDIR */
        change_user(pas);
        if (DebugOpt) {
            crondlog(LVL5 "child running %s", DEFAULT_SHELL);
        }
        /* crond 3.0pl1-100 puts tasks in separate process groups */
        bb_setpgrp();
        execl(DEFAULT_SHELL, DEFAULT_SHELL, "-c", line->cl_cmd, (char *) NULL);
        crondlog(ERR20 "can't execute '%s' for user %s", DEFAULT_SHELL, user);
        _exit(EXIT_SUCCESS);
    }
    if (pid < 0) {
        /* FORK FAILED */
        crondlog(ERR20 "can't vfork");
 err:
        pid = 0;
    }
    line->cl_pid = pid;
}

#define process_finished_job(user, line)  ((line)->cl_pid = 0)

#endif /* !ENABLE_FEATURE_CROND_CALL_SENDMAIL */

/*
 * Determine which jobs need to be run.  Under normal conditions, the
 * period is about a minute (one scan).  Worst case it will be one
 * hour (60 scans).
 */
static void flag_starting_jobs(time_t t1, time_t t2)
{
    time_t t;

    /* Find jobs > t1 and <= t2 */

    for (t = t1 - t1 % 60; t <= t2; t += 60) {
        struct tm *ptm;
        CronFile *file;
        CronLine *line;

        if (t <= t1)
            continue;

        ptm = localtime(&t);
        for (file = G.cron_files; file; file = file->cf_next) {
            if (DebugOpt)
                crondlog(LVL5 "file %s:", file->cf_username);
            if (file->cf_deleted)
                continue;
            for (line = file->cf_lines; line; line = line->cl_next) {
                if (DebugOpt)
                    crondlog(LVL5 " line %s", line->cl_cmd);
                if (line->cl_Mins[ptm->tm_min]
                 && line->cl_Hrs[ptm->tm_hour]
                 && (line->cl_Days[ptm->tm_mday] || line->cl_Dow[ptm->tm_wday])
                 && line->cl_Mons[ptm->tm_mon]
                ) {
                    if (DebugOpt) {
                        crondlog(LVL5 " job: %d %s",
                            (int)line->cl_pid, line->cl_cmd);
                    }
                    if (line->cl_pid > 0) {
                        crondlog(LVL8 "user %s: process already running: %s",
                            file->cf_username, line->cl_cmd);
                    } else if (line->cl_pid == 0) {
                        line->cl_pid = -1;
                        file->cf_wants_starting = 1;
                    }
                }
            }
        }
    }
}

static void start_jobs(void)
{
    CronFile *file;
    CronLine *line;

    for (file = G.cron_files; file; file = file->cf_next) {
        if (!file->cf_wants_starting)
            continue;

        file->cf_wants_starting = 0;
        for (line = file->cf_lines; line; line = line->cl_next) {
            pid_t pid;
            if (line->cl_pid >= 0)
                continue;

            start_one_job(file->cf_username, line);
            pid = line->cl_pid;
            crondlog(LVL8 "USER %s pid %3d cmd %s",
                file->cf_username, (int)pid, line->cl_cmd);
            if (pid < 0) {
                file->cf_wants_starting = 1;
            }
            if (pid > 0) {
                file->cf_has_running = 1;
            }
        }
    }
}

/*
 * Check for job completion, return number of jobs still running after
 * all done.
 */
static int check_completions(void)
{
    CronFile *file;
    CronLine *line;
    int num_still_running = 0;

    for (file = G.cron_files; file; file = file->cf_next) {
        if (!file->cf_has_running)
            continue;

        file->cf_has_running = 0;
        for (line = file->cf_lines; line; line = line->cl_next) {
            int r;

            if (line->cl_pid <= 0)
                continue;

            r = waitpid(line->cl_pid, NULL, WNOHANG);
            if (r < 0 || r == line->cl_pid) {
                process_finished_job(file->cf_username, line);
                if (line->cl_pid == 0) {
                    /* sendmail was not started for it */
                    continue;
                }
                /* else: sendmail was started, job is still running, fall thru */
            }
            /* else: r == 0: "process is still running" */
            file->cf_has_running = 1;
        }
//FIXME: if !file->cf_has_running && file->deleted: delete it!
//otherwise deleted entries will stay forever, right?
        num_still_running += file->cf_has_running;
    }
    return num_still_running;
}

int crond_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int crond_main(int argc UNUSED_PARAM, char **argv)
{
    time_t t2;
    int rescan;
    int sleep_time;
    unsigned opts;

    INIT_G();

    /* "-b after -f is ignored", and so on for every pair a-b */
    opt_complementary = "f-b:b-f:S-L:L-S" IF_FEATURE_CROND_D(":d-l")
            /* -l and -d have numeric param */
            ":l+" IF_FEATURE_CROND_D(":d+");
    opts = getopt32(argv, "l:L:fbSc:" IF_FEATURE_CROND_D("d:"),
            &G.log_level, &G.log_filename, &G.crontab_dir_name
            IF_FEATURE_CROND_D(,&G.log_level));
    /* both -d N and -l N set the same variable: G.log_level */

    if (!(opts & OPT_f)) {
        /* close stdin, stdout, stderr.
         * close unused descriptors - don't need them. */
        bb_daemonize_or_rexec(DAEMON_CLOSE_EXTRA_FDS, argv);
    }

    if (!(opts & OPT_d) && G.log_filename == NULL) {
        /* logging to syslog */
        openlog(applet_name, LOG_CONS | LOG_PID, LOG_CRON);
        logmode = LOGMODE_SYSLOG;
    }

    xchdir(G.crontab_dir_name);
    //signal(SIGHUP, SIG_IGN); /* ? original crond dies on HUP... */
    xsetenv("SHELL", DEFAULT_SHELL); /* once, for all future children */
    crondlog(LVL8 "crond (busybox "BB_VER") started, log level %d", G.log_level);
    rescan_crontab_dir();
    write_pidfile(CONFIG_PID_FILE_PATH "/crond.pid");

    /* Main loop */
    t2 = time(NULL);
    rescan = 60;
    sleep_time = 60;
    for (;;) {
        struct stat sbuf;
        time_t t1;
        long dt;

        t1 = t2;

        /* Synchronize to 1 minute, minimum 1 second */
        sleep(sleep_time - (time(NULL) % sleep_time) + 1);

        t2 = time(NULL);
        dt = (long)t2 - (long)t1;

        /*
         * The file 'cron.update' is checked to determine new cron
         * jobs.  The directory is rescanned once an hour to deal
         * with any screwups.
         *
         * Check for time jump.  Disparities over an hour either way
         * result in resynchronization.  A negative disparity
         * less than an hour causes us to effectively sleep until we
         * match the original time (i.e. no re-execution of jobs that
         * have just been run).  A positive disparity less than
         * an hour causes intermediate jobs to be run, but only once
         * in the worst case.
         *
         * When running jobs, the inequality used is greater but not
         * equal to t1, and less then or equal to t2.
         */
        if (stat(G.crontab_dir_name, &sbuf) != 0)
            sbuf.st_mtime = 0; /* force update (once) if dir was deleted */
        if (G.crontab_dir_mtime != sbuf.st_mtime) {
            G.crontab_dir_mtime = sbuf.st_mtime;
            rescan = 1;
        }
        if (--rescan == 0) {
            rescan = 60;
            rescan_crontab_dir();
        }
        process_cron_update_file();
        if (DebugOpt)
            crondlog(LVL5 "wakeup dt=%ld", dt);
        if (dt < -60 * 60 || dt > 60 * 60) {
            crondlog(WARN9 "time disparity of %ld minutes detected", dt / 60);
            /* and we do not run any jobs in this case */
        } else if (dt > 0) {
            /* Usual case: time advances forward, as expected */
            flag_starting_jobs(t1, t2);
            start_jobs();
            if (check_completions() > 0) {
                /* some jobs are still running */
                sleep_time = 10;
            } else {
                sleep_time = 60;
            }
        }
        /* else: time jumped back, do not run any jobs */
    } /* for (;;) */

    return 0; /* not reached */
}