posix/execlp.c

   1 /* Copyright (C) 1991, 1993, 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 <stddef.h>
  22 #include <string.h>
  23
  24 /* Execute FILE, searching in the `PATH' environment variable if
  25    it contains no slashes, with all arguments after FILE until a
  26    NULL pointer and environment from `environ'.  */
  27 int
  28 execlp (const char *file, const char *arg, ...)
  29 {
  30   size_t argv_max = 1024;
  31   const char **argv = alloca (argv_max * sizeof (const char *));
  32   unsigned int i;
  33   va_list args;
  34
  35   argv[0] = arg;
  36
  37   va_start (args, arg);
  38   i = 1;
  39   do
  40     {
  41       if (i == argv_max)
  42         {
  43           const char **nptr = alloca ((argv_max *= 2) * sizeof (const char *));
  44
  45           if ((char *) nptr + argv_max == (char *) argv)
  46             {
  47               /* Stack grows down.  */
  48               argv = (const char **) memcpy (nptr, argv, i);
  49               argv_max += i;
  50             }
  51           else if ((char *) argv + i == (char *) nptr)
  52             /* Stack grows up.  */
  53             argv_max += i;
  54           else
  55             /* We have a hole in the stack.  */
  56             argv = (const char **) memcpy (nptr, argv, i);
  57         }
  58
  59       argv[i] = va_arg (args, const char *);
  60     }
  61   while (argv[i++] != NULL);
  62   va_end (args);
  63
  64   return execvp (file, (char *const *) argv);
  65 }