posix/execle.c

   1 /* Copyright (C) 1991, 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 PATH with all arguments after PATH until a NULL pointer,
  25    and the argument after that for environment.  */
  26 int
  27 execle (const char *path, const char *arg, ...)
  28 {
  29   size_t argv_max = 1024;
  30   const char **argv = alloca (argv_max * sizeof (const char *));
  31   const char *const *envp;
  32   unsigned int i;
  33   va_list args;
  34   argv[0] = arg;
  35
  36   va_start(args, arg);
  37   i = 1;
  38   do
  39     {
  40       if (i == argv_max)
  41         {
  42           const char **nptr = alloca ((argv_max *= 2) * sizeof (const char *));
  43
  44           if ((char *) nptr + argv_max == (char *) argv)
  45             {
  46               /* Stack grows down.  */
  47               argv = (const char **) memcpy (nptr, argv, i);
  48               argv_max += i;
  49             }
  50           else if ((char *) argv + i == (char *) nptr)
  51             /* Stack grows up.  */
  52             argv_max += i;
  53           else
  54             /* We have a hole in the stack.  */
  55             argv = (const char **) memcpy (nptr, argv, i);
  56         }
  57
  58       argv[i] = va_arg (args, const char *);
  59     }
  60   while (argv[i++] != NULL);
  61
  62   envp = va_arg(args, const char *const *);
  63   va_end(args);
  64
  65   return __execve(path, (char *const *) argv, (char *const *) envp);
  66 }