libbb/executable.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * Utility routines.
   4  *
   5  * Copyright (C) 2006 Gabriel Somlo <somlo at cmu.edu>
   6  *
   7  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   8  */
   9 #include "libbb.h"
  10
  11 /* check if path points to an executable file;
  12  * return 1 if found;
  13  * return 0 otherwise;
  14  */
  15 int FAST_FUNC file_is_executable(const char *name)
  16 {
  17         struct stat s;
  18         return (!access(name, X_OK) && !stat(name, &s) && S_ISREG(s.st_mode));
  19 }
  20
  21 /* search (*PATHp) for an executable file;
  22  * return allocated string containing full path if found;
  23  *  PATHp points to the component after the one where it was found
  24  *  (or NULL),
  25  *  you may call find_executable again with this PATHp to continue
  26  *  (if it's not NULL).
  27  * return NULL otherwise; (PATHp is undefined)
  28  * in all cases (*PATHp) contents are temporarily modified
  29  * but are restored on return (s/:/NUL/ and back).
  30  */
  31 char* FAST_FUNC find_executable(const char *filename, char **PATHp)
  32 {
  33         /* About empty components in $PATH:
  34          * http://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap08.html
  35          * 8.3 Other Environment Variables - PATH
  36          * A zero-length prefix is a legacy feature that indicates the current
  37          * working directory. It appears as two adjacent colons ( "::" ), as an
  38          * initial colon preceding the rest of the list, or as a trailing colon
  39          * following the rest of the list.
  40          */
  41         char *p, *n;
  42
  43         p = *PATHp;
  44         while (p) {
  45                 int ex;
  46
  47                 n = strchr(p, ':');
  48                 if (n) *n = '\0';
  49                 p = concat_path_file(
  50                         p[0] ? p : ".", /* handle "::" case */
  51                         filename
  52                 );
  53                 ex = file_is_executable(p);
  54                 if (n) *n++ = ':';
  55                 if (ex) {
  56                         *PATHp = n;
  57                         return p;
  58                 }
  59                 free(p);
  60                 p = n;
  61         } /* on loop exit p == NULL */
  62         return p;
  63 }
  64
  65 /* search $PATH for an executable file;
  66  * return 1 if found;
  67  * return 0 otherwise;
  68  */
  69 int FAST_FUNC executable_exists(const char *filename)
  70 {
  71         char *path = getenv("PATH");
  72         char *ret = find_executable(filename, &path);
  73         free(ret);
  74         return ret != NULL;
  75 }
  76
  77 #if ENABLE_FEATURE_PREFER_APPLETS
  78 /* just like the real execvp, but try to launch an applet named 'file' first */
  79 int FAST_FUNC BB_EXECVP(const char *file, char *const argv[])
  80 {
  81         if (find_applet_by_name(file) >= 0)
  82                 execvp(bb_busybox_exec_path, argv);
  83         return execvp(file, argv);
  84 }
  85 #endif
  86
  87 void FAST_FUNC BB_EXECVP_or_die(char **argv)
  88 {
  89         BB_EXECVP(argv[0], argv);
  90         /* SUSv3-mandated exit codes */
  91         xfunc_error_retval = (errno == ENOENT) ? 127 : 126;
  92         bb_perror_msg_and_die("can't execute '%s'", argv[0]);
  93 }