posix/execvp.c

   1 /* Copyright (C) 1991, 1992, 1995, 1996 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 <unistd.h>
  20 #include <stdarg.h>
  21 #include <stdlib.h>
  22 #include <string.h>
  23 #include <errno.h>
  24 #include <paths.h>
  25
  26 /* Execute FILE, searching in the `PATH' environment variable if it contains
  27    no slashes, with arguments ARGV and environment from `environ'.  */
  28 int
  29 execvp (file, argv)
  30      const char *file;
  31      char *const argv[];
  32 {
  33   int got_eacces = 0;
  34
  35   void execute (const char *file, char *const argv[])
  36     {
  37       execv (file, argv);
  38
  39       if (errno == ENOEXEC)
  40         {
  41           /* The file is accessible but it is not an executable file.
  42              Invoke the shell to interpret it as a script.  */
  43
  44           /* Count the arguments.  */
  45           int argc = 0;
  46           while (argv[argc++])
  47             ;
  48
  49           /* Construct an argument list for the shell.  */
  50           {
  51             char *new_argv[argc + 1];
  52             new_argv[0] = (char *) _PATH_BSHELL;
  53             new_argv[1] = (char *) file;
  54             while (argc > 1)
  55               {
  56                 new_argv[argc] = argv[argc - 1];
  57                 --argc;
  58               }
  59
  60             /* Execute the shell.  */
  61             execv (new_argv[0], new_argv);
  62           }
  63         }
  64     }
  65
  66   if (strchr (file, '/') != NULL)
  67     /* Don't search when it contains a slash.  */
  68     execute (file, argv);
  69   else
  70     {
  71       char *path, *p, *name;
  72       size_t len;
  73
  74       path = getenv ("PATH");
  75       if (path == NULL)
  76         {
  77           /* There is no `PATH' in the environment.
  78              The default search path is the current directory
  79              followed by the path `confstr' returns for `_CS_PATH'.  */
  80           len = confstr (_CS_PATH, (char *) NULL, 0);
  81           path = (char *) __alloca (1 + len);
  82           path[0] = ':';
  83           (void) confstr (_CS_PATH, path + 1, len);
  84         }
  85
  86       len = strlen (file) + 1;
  87       name = __alloca (strlen (path) + len);
  88       p = path;
  89       do
  90         {
  91           path = p;
  92           p = strchr (path, ':');
  93           if (p == NULL)
  94             p = strchr (path, '\0');
  95
  96           if (p == path)
  97             /* Two adjacent colons, or a colon at the beginning or the end
  98                of `PATH' means to search the current directory.  */
  99             (void) memcpy (name, file, len);
 100           else
 101             {
 102               /* Construct the pathname to try.  */
 103               (void) memcpy (name, path, p - path);
 104               name[p - path] = '/';
 105               (void) memcpy (&name[(p - path) + 1], file, len);
 106             }
 107
 108           /* Try to execute this name.  If it works, execv will not return.  */
 109           execute (name, argv);
 110
 111           switch (errno)
 112             {
 113             case EACCES:
 114               /* Record the we got a `Permission denied' error.  If we end
 115                  up finding no executable we can use, we want to diagnose
 116                  that we did find one but were denied access.  */
 117               got_eacces = 1;
 118             case ENOENT:
 119               /* Those errors indicate the file is missing or not executable
 120                  by us, in which case we want to just try the next path
 121                  directory.  */
 122               break;
 123
 124             default:
 125               /* Some other error means we found an executable file, but
 126                  something went wrong executing it; return the error to our
 127                  caller.  */
 128               return -1;
 129             }
 130         }
 131       while (*p++ != '\0');
 132     }
 133
 134   /* We tried every element and none of them worked.  */
 135
 136   if (got_eacces)
 137     /* At least one failure was due to permissions, so report that error.  */
 138     errno = EACCES;
 139
 140   /* Return the error from the last attempt (probably ENOENT).  */
 141   return -1;
 142 }