posix/execvp.c

   1 /* Copyright (C) 1991, 1992 Free Software Foundation, Inc.
   2 This file is part of the GNU C Library.
   3
   4 The GNU C Library is free software; you can redistribute it and/or
   5 modify it under the terms of the GNU Library General Public License as
   6 published by the Free Software Foundation; either version 2 of the
   7 License, or (at your option) any later version.
   8
   9 The GNU C Library is distributed in the hope that it will be useful,
  10 but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12 Library General Public License for more details.
  13
  14 You should have received a copy of the GNU Library General Public
  15 License along with the GNU C Library; see the file COPYING.LIB.  If
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, USA.  */
  18
  19 #include <ansidecl.h>
  20 #include <unistd.h>
  21 #include <stdarg.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <sys/stat.h>
  25 #include <limits.h>
  26 #include <sys/types.h>
  27
  28 #ifndef HAVE_GNU_LD
  29 #define __environ       environ
  30 #endif
  31
  32 /* Execute FILE, searching in the `PATH' environment variable if it contains
  33    no slashes, with arguments ARGV and environment from `environ'.  */
  34 int
  35 DEFUN(execvp, (file, argv), CONST char *file AND char *CONST argv[])
  36 {
  37   if (strchr (file, '/') == NULL)
  38     {
  39       char *path, *p;
  40       struct stat st;
  41       size_t len;
  42       uid_t uid;
  43       gid_t gid;
  44       int ngroups;
  45       gid_t groups[NGROUPS_MAX];
  46       char *name;
  47
  48       path = getenv ("PATH");
  49       if (path == NULL)
  50         {
  51           /* There is no `PATH' in the environment.
  52              The default search path is the current directory
  53              followed by the path `confstr' returns for `_CS_PATH'.  */
  54           len = confstr (_CS_PATH, (char *) NULL, 0);
  55           path = (char *) __alloca (1 + len);
  56           path[0] = ':';
  57           (void) confstr (_CS_PATH, path + 1, len);
  58         }
  59
  60       len = strlen (file) + 1;
  61       name = __alloca (strlen (path) + len);
  62       uid = geteuid ();
  63       gid = getegid ();
  64       ngroups = getgroups (sizeof (groups) / sizeof (groups[0]), groups);
  65       p = path;
  66       do
  67         {
  68           path = p;
  69           p = strchr (path, ':');
  70           if (p == NULL)
  71             p = strchr (path, '\0');
  72
  73           if (p == path)
  74             /* Two adjacent colons, or a colon at the beginning or the end
  75                of `PATH' means to search the current directory.  */
  76             (void) memcpy (name, file, len);
  77           else
  78             {
  79               /* Construct the pathname to try.  */
  80               (void) memcpy (name, path, p - path);
  81               name[p - path] = '/';
  82               (void) memcpy (&name[(p - path) + 1], file, len);
  83             }
  84           if (stat (name, &st) == 0 && S_ISREG (st.st_mode))
  85             {
  86               int bit = S_IXOTH;
  87               if (st.st_uid == uid)
  88                 bit = S_IXUSR;
  89               else if (st.st_gid == gid)
  90                 bit = S_IXGRP;
  91               else
  92                 {
  93                   register int i;
  94                   for (i = 0; i < ngroups; ++i)
  95                     if (st.st_gid == groups[i])
  96                       {
  97                         bit = S_IXGRP;
  98                         break;
  99                       }
 100                 }
 101               if (st.st_mode & bit)
 102                 {
 103                   file = name;
 104                   break;
 105                 }
 106             }
 107         }
 108       while (*p++ != '\0');
 109     }
 110
 111   return __execve (file, argv, __environ);
 112 }