posix/execlp.c

   1 /* Copyright (C) 1991, 1993, 1996, 1997, 1998 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 <alloca.h>
  20 #include <unistd.h>
  21 #include <stdarg.h>
  22 #include <stddef.h>
  23 #include <string.h>
  24
  25 /* Execute FILE, searching in the `PATH' environment variable if
  26    it contains no slashes, with all arguments after FILE until a
  27    NULL pointer and environment from `environ'.  */
  28 int
  29 execlp (const char *file, const char *arg, ...)
  30 {
  31   size_t argv_max = 1024;
  32   const char **argv = alloca (argv_max * sizeof (const char *));
  33   unsigned int i;
  34   va_list args;
  35
  36   argv[0] = arg;
  37
  38   va_start (args, arg);
  39   i = 0;
  40   while (argv[i++] != NULL)
  41     {
  42       if (i == argv_max)
  43         {
  44           const char **nptr = alloca ((argv_max *= 2) * sizeof (const char *));
  45
  46           if ((char *) nptr + argv_max == (char *) argv)
  47             {
  48               /* Stack grows down.  */
  49               argv = (const char **) memcpy (nptr, argv, i);
  50               argv_max += i;
  51             }
  52           else if ((char *) argv + i == (char *) nptr)
  53             /* Stack grows up.  */
  54             argv_max += i;
  55           else
  56             /* We have a hole in the stack.  */
  57             argv = (const char **) memcpy (nptr, argv, i);
  58         }
  59
  60       argv[i] = va_arg (args, const char *);
  61     }
  62   va_end (args);
  63
  64   return execvp (file, (char *const *) argv);
  65 }