source: MondoRescue/branches/3.3/mindi-busybox/libbb/executable.c@ 3621

/* vi: set sw=4 ts=4: */
/*
 * Utility routines.
 *
 * Copyright (C) 2006 Gabriel Somlo <somlo at cmu.edu>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */

#include "libbb.h"

/* check if path points to an executable file;
 * return 1 if found;
 * return 0 otherwise;
 */
int FAST_FUNC file_is_executable(const char *name)
{
    struct stat s;
    return (!access(name, X_OK) && !stat(name, &s) && S_ISREG(s.st_mode));
}

/* search (*PATHp) for an executable file;
 * return allocated string containing full path if found;
 *  PATHp points to the component after the one where it was found
 *  (or NULL),
 *  you may call find_executable again with this PATHp to continue
 *  (if it's not NULL).
 * return NULL otherwise; (PATHp is undefined)
 * in all cases (*PATHp) contents will be trashed (s/:/NUL/).
 */
char* FAST_FUNC find_executable(const char *filename, char **PATHp)
{
    /* About empty components in $PATH:
     * http://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap08.html
     * 8.3 Other Environment Variables - PATH
     * A zero-length prefix is a legacy feature that indicates the current
     * working directory. It appears as two adjacent colons ( "::" ), as an
     * initial colon preceding the rest of the list, or as a trailing colon
     * following the rest of the list.
     */
    char *p, *n;

    p = *PATHp;
    while (p) {
        n = strchr(p, ':');
        if (n)
            *n++ = '\0';
        p = concat_path_file(
            p[0] ? p : ".", /* handle "::" case */
            filename
        );
        if (file_is_executable(p)) {
            *PATHp = n;
            return p;
        }
        free(p);
        p = n;
    } /* on loop exit p == NULL */
    return p;
}

/* search $PATH for an executable file;
 * return 1 if found;
 * return 0 otherwise;
 */
int FAST_FUNC executable_exists(const char *filename)
{
    char *path = xstrdup(getenv("PATH"));
    char *tmp = path;
    char *ret = find_executable(filename, &tmp);
    free(path);
    free(ret);
    return ret != NULL;
}

#if ENABLE_FEATURE_PREFER_APPLETS
/* just like the real execvp, but try to launch an applet named 'file' first */
int FAST_FUNC BB_EXECVP(const char *file, char *const argv[])
{
    if (find_applet_by_name(file) >= 0)
        execvp(bb_busybox_exec_path, argv);
    return execvp(file, argv);
}
#endif

void FAST_FUNC BB_EXECVP_or_die(char **argv)
{
    BB_EXECVP(argv[0], argv);
    /* SUSv3-mandated exit codes */
    xfunc_error_retval = (errno == ENOENT) ? 127 : 126;
    bb_perror_msg_and_die("can't execute '%s'", argv[0]);
}

/* Typical idiom for applets which exec *optional* PROG [ARGS] */
void FAST_FUNC exec_prog_or_SHELL(char **argv)
{
    if (argv[0]) {
        BB_EXECVP_or_die(argv);
    }
    run_shell(getenv("SHELL"), /*login:*/ 1, NULL, NULL);
}