glibc/posix/execlp.c

/* Copyright (C) 1991, 1993, 1996, 1997, 1998 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include <alloca.h>
#include <unistd.h>
#include <stdarg.h>
#include <stddef.h>
#include <string.h>

/* Execute FILE, searching in the `PATH' environment variable if
   it contains no slashes, with all arguments after FILE until a
   NULL pointer and environment from `environ'.  */
int
execlp (const char *file, const char *arg, ...)
{
  size_t argv_max = 1024;
  const char **argv = alloca (argv_max * sizeof (const char *));
  unsigned int i;
  va_list args;

  argv[0] = arg;

  va_start (args, arg);
  i = 0;
  while (argv[i++] != NULL)
    {
      if (i == argv_max)
	{
	  const char **nptr = alloca ((argv_max *= 2) * sizeof (const char *));

	  if ((char *) nptr + argv_max == (char *) argv)
	    {
	      /* Stack grows down.  */
	      argv = (const char **) memcpy (nptr, argv, i);
	      argv_max += i;
	    }
	  else if ((char *) argv + i == (char *) nptr)
	    /* Stack grows up.  */
	    argv_max += i;
	  else
	    /* We have a hole in the stack.  */
	    argv = (const char **) memcpy (nptr, argv, i);
	}

      argv[i] = va_arg (args, const char *);
    }
  va_end (args);

  return execvp (file, (char *const *) argv);
}