posix/execvp.c

   1 /* Copyright (C) 1991, 92, 95, 96, 97, 98, 99 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 not,
  16    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17    Boston, MA 02111-1307, USA.  */
  18
  19 #include <unistd.h>
  20 #include <stdarg.h>
  21 #include <stdlib.h>
  22 #include <string.h>
  23 #include <errno.h>
  24 #include <paths.h>
  25
  26
  27 /* The file is accessible but it is not an executable file.  Invoke
  28    the shell to interpret it as a script.  */
  29 static void
  30 internal_function
  31 script_execute (const char *file, char *const argv[])
  32 {
  33   /* Count the arguments.  */
  34   int argc = 0;
  35   while (argv[argc++])
  36     ;
  37
  38   /* Construct an argument list for the shell.  */
  39   {
  40     char *new_argv[argc + 1];
  41     new_argv[0] = (char *) _PATH_BSHELL;
  42     new_argv[1] = (char *) file;
  43     while (argc > 1)
  44       {
  45         new_argv[argc] = argv[argc - 1];
  46         --argc;
  47       }
  48
  49     /* Execute the shell.  */
  50     __execve (new_argv[0], new_argv, __environ);
  51   }
  52 }
  53
  54
  55 /* Execute FILE, searching in the `PATH' environment variable if it contains
  56    no slashes, with arguments ARGV and environment from `environ'.  */
  57 int
  58 execvp (file, argv)
  59      const char *file;
  60      char *const argv[];
  61 {
  62   if (*file == '\0')
  63     {
  64       /* We check the simple case first. */
  65       __set_errno (ENOENT);
  66       return -1;
  67     }
  68
  69   if (strchr (file, '/') != NULL)
  70     {
  71       /* Don't search when it contains a slash.  */
  72       __execve (file, argv, __environ);
  73
  74       if (errno == ENOEXEC)
  75         script_execute (file, argv);
  76     }
  77   else
  78     {
  79       int got_eacces = 0;
  80       char *path, *p, *name;
  81       size_t len;
  82       size_t pathlen;
  83
  84       path = getenv ("PATH");
  85       if (path == NULL)
  86         {
  87           /* There is no `PATH' in the environment.
  88              The default search path is the current directory
  89              followed by the path `confstr' returns for `_CS_PATH'.  */
  90           len = confstr (_CS_PATH, (char *) NULL, 0);
  91           path = (char *) __alloca (1 + len);
  92           path[0] = ':';
  93           (void) confstr (_CS_PATH, path + 1, len);
  94         }
  95
  96       len = strlen (file) + 1;
  97       pathlen = strlen (path);
  98       name = __alloca (pathlen + len + 1);
  99       /* Copy the file name at the top.  */
 100       name = (char *) memcpy (name + pathlen + 1, file, len);
 101       /* And add the slash.  */
 102       *--name = '/';
 103
 104       p = path;
 105       do
 106         {
 107           char *startp;
 108
 109           path = p;
 110           p = __strchrnul (path, ':');
 111
 112           if (p == path)
 113             /* Two adjacent colons, or a colon at the beginning or the end
 114                of `PATH' means to search the current directory.  */
 115             startp = name + 1;
 116           else
 117             startp = (char *) memcpy (name - (p - path), path, p - path);
 118
 119           /* Try to execute this name.  If it works, execv will not return.  */
 120           __execve (startp, argv, __environ);
 121
 122           if (errno == ENOEXEC)
 123             script_execute (startp, argv);
 124
 125           switch (errno)
 126             {
 127             case EACCES:
 128               /* Record the we got a `Permission denied' error.  If we end
 129                  up finding no executable we can use, we want to diagnose
 130                  that we did find one but were denied access.  */
 131               got_eacces = 1;
 132             case ENOENT:
 133             case ESTALE:
 134             case ENOTDIR:
 135               /* Those errors indicate the file is missing or not executable
 136                  by us, in which case we want to just try the next path
 137                  directory.  */
 138               break;
 139
 140             default:
 141               /* Some other error means we found an executable file, but
 142                  something went wrong executing it; return the error to our
 143                  caller.  */
 144               return -1;
 145             }
 146         }
 147       while (*p++ != '\0');
 148
 149       /* We tried every element and none of them worked.  */
 150       if (got_eacces)
 151         /* At least one failure was due to permissions, so report that
 152            error.  */
 153         __set_errno (EACCES);
 154     }
 155
 156   /* Return the error from the last attempt (probably ENOENT).  */
 157   return -1;
 158 }