posix/execvp.c

   1 /* Copyright (C) 1991,92,1995-99,2002,2004,2005 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 Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the 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    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #include <unistd.h>
  20 #include <stdarg.h>
  21 #include <stdbool.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <errno.h>
  25 #include <paths.h>
  26
  27
  28 /* The file is accessible but it is not an executable file.  Invoke
  29    the shell to interpret it as a script.  */
  30 static char **
  31 internal_function
  32 allocate_scripts_argv (const char *file, char *const argv[])
  33 {
  34   /* Count the arguments.  */
  35   int argc = 0;
  36   while (argv[argc++])
  37     ;
  38
  39   /* Construct an argument list for the shell.  */
  40   char **new_argv = (char **) malloc ((argc + 1) * sizeof (char *));
  41   if (new_argv != NULL)
  42     {
  43       new_argv[0] = (char *) _PATH_BSHELL;
  44       new_argv[1] = (char *) file;
  45       while (argc > 1)
  46         {
  47           new_argv[argc] = argv[argc - 1];
  48           --argc;
  49         }
  50     }
  51
  52   return new_argv;
  53 }
  54
  55
  56 /* Execute FILE, searching in the `PATH' environment variable if it contains
  57    no slashes, with arguments ARGV and environment from `environ'.  */
  58 int
  59 execvp (file, argv)
  60      const char *file;
  61      char *const argv[];
  62 {
  63   if (*file == '\0')
  64     {
  65       /* We check the simple case first. */
  66       __set_errno (ENOENT);
  67       return -1;
  68     }
  69
  70   char **script_argv = NULL;
  71
  72   if (strchr (file, '/') != NULL)
  73     {
  74       /* Don't search when it contains a slash.  */
  75       __execve (file, argv, __environ);
  76
  77       if (errno == ENOEXEC)
  78         {
  79           script_argv = allocate_scripts_argv (file, argv);
  80           if (script_argv != NULL)
  81             {
  82               __execve (script_argv[0], script_argv, __environ);
  83
  84               free (script_argv);
  85             }
  86         }
  87     }
  88   else
  89     {
  90       char *path = getenv ("PATH");
  91       bool path_malloc = false;
  92       if (path == NULL)
  93         {
  94           /* There is no `PATH' in the environment.
  95              The default search path is the current directory
  96              followed by the path `confstr' returns for `_CS_PATH'.  */
  97           size_t len = confstr (_CS_PATH, (char *) NULL, 0);
  98           path = (char *) malloc (1 + len);
  99           if (path == NULL)
 100             return -1;
 101           path[0] = ':';
 102           (void) confstr (_CS_PATH, path + 1, len);
 103           path_malloc = true;
 104         }
 105
 106       size_t len = strlen (file) + 1;
 107       size_t pathlen = strlen (path);
 108       char *name = malloc (pathlen + len + 1);
 109       if (name == NULL)
 110         {
 111           if (path_malloc)
 112             free (path);
 113           return -1;
 114         }
 115       /* Copy the file name at the top.  */
 116       name = (char *) memcpy (name + pathlen + 1, file, len);
 117       /* And add the slash.  */
 118       *--name = '/';
 119
 120       bool got_eacces = false;
 121       char *p = path;
 122       do
 123         {
 124           char *startp;
 125
 126           path = p;
 127           p = __strchrnul (path, ':');
 128
 129           if (p == path)
 130             /* Two adjacent colons, or a colon at the beginning or the end
 131                of `PATH' means to search the current directory.  */
 132             startp = name + 1;
 133           else
 134             startp = (char *) memcpy (name - (p - path), path, p - path);
 135
 136           /* Try to execute this name.  If it works, execv will not return.  */
 137           __execve (startp, argv, __environ);
 138
 139           if (errno == ENOEXEC)
 140             {
 141               if (script_argv == NULL)
 142                 {
 143                   script_argv = allocate_scripts_argv (file, argv);
 144                   if (script_argv == NULL)
 145                     {
 146                       /* A possible EACCES error is not as important as
 147                          the ENOMEM.  */
 148                       got_eacces = false;
 149                       break;
 150                     }
 151                 }
 152
 153               __execve (script_argv[0], script_argv, __environ);
 154             }
 155
 156           switch (errno)
 157             {
 158             case EACCES:
 159               /* Record the we got a `Permission denied' error.  If we end
 160                  up finding no executable we can use, we want to diagnose
 161                  that we did find one but were denied access.  */
 162               got_eacces = true;
 163             case ENOENT:
 164             case ESTALE:
 165             case ENOTDIR:
 166               /* Those errors indicate the file is missing or not executable
 167                  by us, in which case we want to just try the next path
 168                  directory.  */
 169             case ENODEV:
 170             case ETIMEDOUT:
 171               /* Some strange filesystems like AFS return even
 172                  stranger error numbers.  They cannot reasonably mean
 173                  anything else so ignore those, too.  */
 174               break;
 175
 176             default:
 177               /* Some other error means we found an executable file, but
 178                  something went wrong executing it; return the error to our
 179                  caller.  */
 180               return -1;
 181             }
 182         }
 183       while (*p++ != '\0');
 184
 185       /* We tried every element and none of them worked.  */
 186       if (got_eacces)
 187         /* At least one failure was due to permissions, so report that
 188            error.  */
 189         __set_errno (EACCES);
 190
 191       free (script_argv);
 192       free (name);
 193       if (path_malloc)
 194         free (path);
 195     }
 196
 197   /* Return the error from the last attempt (probably ENOENT).  */
 198   return -1;
 199 }
 200 libc_hidden_def (execvp)