posix/execvp.c

   1 /* Copyright (C) 1991, 1992, 1995, 1996, 1997 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 static void
  28 internal_function
  29 execute (const char *file, char *const argv[])
  30 {
  31   execv (file, argv);
  32
  33   if (errno == ENOEXEC)
  34     {
  35       /* The file is accessible but it is not an executable file.
  36          Invoke the shell to interpret it as a script.  */
  37
  38       /* Count the arguments.  */
  39       int argc = 0;
  40       while (argv[argc++])
  41         ;
  42
  43       /* Construct an argument list for the shell.  */
  44       {
  45         char *new_argv[argc + 1];
  46         new_argv[0] = (char *) _PATH_BSHELL;
  47         new_argv[1] = (char *) file;
  48         while (argc > 1)
  49           {
  50             new_argv[argc] = argv[argc - 1];
  51             --argc;
  52           }
  53
  54         /* Execute the shell.  */
  55         execv (new_argv[0], new_argv);
  56       }
  57         }
  58 }
  59
  60
  61 /* Execute FILE, searching in the `PATH' environment variable if it contains
  62    no slashes, with arguments ARGV and environment from `environ'.  */
  63 int
  64 execvp (file, argv)
  65      const char *file;
  66      char *const argv[];
  67 {
  68   int got_eacces = 0;
  69
  70   if (strchr (file, '/') != NULL)
  71     /* Don't search when it contains a slash.  */
  72     execute (file, argv);
  73   else
  74     {
  75       char *path, *p, *name;
  76       size_t len;
  77
  78       path = getenv ("PATH");
  79       if (path == NULL)
  80         {
  81           /* There is no `PATH' in the environment.
  82              The default search path is the current directory
  83              followed by the path `confstr' returns for `_CS_PATH'.  */
  84           len = confstr (_CS_PATH, (char *) NULL, 0);
  85           path = (char *) __alloca (1 + len);
  86           path[0] = ':';
  87           (void) confstr (_CS_PATH, path + 1, len);
  88         }
  89
  90       len = strlen (file) + 1;
  91       name = __alloca (strlen (path) + len);
  92       p = path;
  93       do
  94         {
  95           path = p;
  96           p = strchr (path, ':');
  97           if (p == NULL)
  98             p = strchr (path, '\0');
  99
 100           if (p == path)
 101             /* Two adjacent colons, or a colon at the beginning or the end
 102                of `PATH' means to search the current directory.  */
 103             (void) memcpy (name, file, len);
 104           else
 105             {
 106               /* Construct the pathname to try.  */
 107               char *tmp = __mempcpy (name, path, p - path);
 108               *tmp++ = '/';
 109               (void) __mempcpy (tmp, file, len);
 110             }
 111
 112           /* Try to execute this name.  If it works, execv will not return.  */
 113           execute (name, argv);
 114
 115           switch (errno)
 116             {
 117             case EACCES:
 118               /* Record the we got a `Permission denied' error.  If we end
 119                  up finding no executable we can use, we want to diagnose
 120                  that we did find one but were denied access.  */
 121               got_eacces = 1;
 122             case ENOENT:
 123             case ESTALE:
 124               /* Those errors indicate the file is missing or not executable
 125                  by us, in which case we want to just try the next path
 126                  directory.  */
 127               break;
 128
 129             default:
 130               /* Some other error means we found an executable file, but
 131                  something went wrong executing it; return the error to our
 132                  caller.  */
 133               return -1;
 134             }
 135         }
 136       while (*p++ != '\0');
 137     }
 138
 139   /* We tried every element and none of them worked.  */
 140
 141   if (got_eacces)
 142     /* At least one failure was due to permissions, so report that error.  */
 143     __set_errno (EACCES);
 144
 145   /* Return the error from the last attempt (probably ENOENT).  */
 146   return -1;
 147 }