source: MondoRescue/branches/2.2.5/mindi-busybox/libbb/execable.c

/* 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 tarball for details.
 */

#include "libbb.h"

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

/* search $PATH for an executable file;
 * return allocated string containing full path if found;
 * return NULL otherwise;
 */
char *find_execable(const char *filename)
{
    char *path, *p, *n;

    p = path = xstrdup(getenv("PATH"));
    while (p) {
        n = strchr(p, ':');
        if (n)
            *n++ = '\0';
        if (*p != '\0') { /* it's not a PATH="foo::bar" situation */
            p = concat_path_file(p, filename);
            if (execable_file(p)) {
                free(path);
                return p;
            }
            free(p);
        }
        p = n;
    }
    free(path);
    return NULL;
}

/* search $PATH for an executable file;
 * return 1 if found;
 * return 0 otherwise;
 */
int exists_execable(const char *filename)
{
    char *ret = find_execable(filename);
    if (ret) {
        free(ret);
        return 1;
    }
    return 0;
}

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