posix/execvp.c

   1 /* Copyright (C) 1991, 1992, 1995 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
  24 /* Execute FILE, searching in the `PATH' environment variable if it contains
  25    no slashes, with arguments ARGV and environment from `environ'.  */
  26 int
  27 execvp (file, argv)
  28      const char *file;
  29      char *const argv[];
  30 {
  31   if (strchr (file, '/') != NULL)
  32     /* Don't search when it contains a slash.  */
  33     return execv (file, argv);
  34   else
  35     {
  36       char *path, *p, *name;
  37       size_t len;
  38
  39       path = getenv ("PATH");
  40       if (path == NULL)
  41         {
  42           /* There is no `PATH' in the environment.
  43              The default search path is the current directory
  44              followed by the path `confstr' returns for `_CS_PATH'.  */
  45           len = confstr (_CS_PATH, (char *) NULL, 0);
  46           path = (char *) __alloca (1 + len);
  47           path[0] = ':';
  48           (void) confstr (_CS_PATH, path + 1, len);
  49         }
  50
  51       len = strlen (file) + 1;
  52       name = __alloca (strlen (path) + len);
  53       p = path;
  54       do
  55         {
  56           path = p;
  57           p = strchr (path, ':');
  58           if (p == NULL)
  59             p = strchr (path, '\0');
  60
  61           if (p == path)
  62             /* Two adjacent colons, or a colon at the beginning or the end
  63                of `PATH' means to search the current directory.  */
  64             (void) memcpy (name, file, len);
  65           else
  66             {
  67               /* Construct the pathname to try.  */
  68               (void) memcpy (name, path, p - path);
  69               name[p - path] = '/';
  70               (void) memcpy (&name[(p - path) + 1], file, len);
  71             }
  72
  73           /* Try to execute this name.  If it works, execv will not return.  */
  74           execv (name, argv);
  75           if (errno != ENOENT && errno != EACCES)
  76             /* Those errors indicate the file is missing or not executable
  77                by us, in which case we want to just try the next path
  78                directory.  Some other error means we found an executable
  79                file, but something went wrong executing it; return the
  80                error to our caller.  */
  81             return -1;
  82         }
  83       while (*p++ != '\0');
  84     }
  85
  86   /* We tried every element and none of them worked.
  87      Return the error from the last attempt (probably ENOENT).  */
  88   return -1;
  89 }