/*
 * Copyright (c) 2000, Amnon BARAK (amnon@cs.huji.ac.il). All rights reserved.
 *
 * Permission to use, copy and distribute this software is hereby granted 
 * under the terms of version 2 or any later version of the GNU General Public
 * License, as published by the Free Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED IN ITS "AS IS" CONDITION, WITH NO WARRANTY
 * WHATSOEVER. NO LIABILITY OF ANY KIND FOR ANY DAMAGES WHATSOEVER RESULTING
 * FROM THE USE OF THIS SOFTWARE WILL BE ACCEPTED.
 */

/*  Adapted to OpenMosix from Mosix and bugfixing by David Santo Orcero */
/*  irbis@orcero.org  http://www.orcero.org/irbis                       */
/* Mosix is (c) of prof. Amnon Barak http://www.mosix.org               */
/* Original code is (c) of prof. Amnon Barak http://www.mosix.org       */
/* OpenMosix is (c) of Moshe Bar http://www.openmosix.com               */
/* Each respective trademark is of its own owner                        */
/* All rights reserved.                                                 */
/* This software is distributed under GPL 2                             */

/* THIS SOFTWARE IS PROVIDED "AS IS". NO WARRANTY IS ASSUMED.               */
/* NO LIABILITY OF ANY KIND FOR ANY DAMAGES WHATSOEVER RESULTING            */
/* FROM THE USE OF THIS SOFTWARE WILL BE ACCEPTED. IT CAN BURN              */
/* YOUR HARD DISK, ERASE ALL YOUR DATA AND BROKE DOWN YOUR                  */
/* MICROWAVE OVEN. YOU ARE ADVISED.                                         */


/*
 * Author(s): Ariel Eizenberg
 */

/* Based on glibc2.1.3 */

#include <stddef.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
#include <signal.h>
#include <sys/types.h>
#include <errno.h>

#define set_errno(Val) errno = (Val)

#define SHELL_PATH      "/bin/sh"       /* Path of the shell.  */
#define SHELL_NAME      "sh"            /* Name to give it.  */

int system (const char *line)
{
  int status, save;
  pid_t pid;
  struct sigaction sa, intr, quit;
  sigset_t block, omask;

  if (line == NULL)
    /* Check that we have a command processor available.  It might
       not be available after a chroot(), for example.  */
    return system("exit 0") == 0;

  sa.sa_handler = SIG_IGN;
  sa.sa_flags = 0;
  sigemptyset (&sa.sa_mask);
  
  if (sigaction (SIGINT, &sa, &intr) < 0)
    return -1;
  if (sigaction (SIGQUIT, &sa, &quit) < 0)
  {
    save = errno;
    (void) sigaction (SIGINT, &intr, (struct sigaction *) NULL);
    set_errno(save);
    return -1;
  }
  
  sigemptyset (&block);
  sigaddset (&block, SIGCHLD);
  save = errno;
  if (sigprocmask (SIG_BLOCK, &block, &omask) < 0)
  {
    if (errno == ENOSYS)
      set_errno (save);
    else
    {
      save = errno;
      (void) sigaction (SIGINT, &intr, (struct sigaction *) NULL);
      (void) sigaction (SIGQUIT, &quit, (struct sigaction *) NULL);
      set_errno (save);
      return -1;
    }
  }

  pid = fork ();/* use vfork instead of fork */
  if (pid == (pid_t) 0)
  {
    /* Child side.  */
    const char *new_argv[4];
    new_argv[0] = SHELL_NAME;
    new_argv[1] = "-c";
    new_argv[2] = line;
    new_argv[3] = NULL;
    
    /* Restore the signals.  */
    (void) sigaction (SIGINT, &intr, (struct sigaction *) NULL);
    (void) sigaction (SIGQUIT, &quit, (struct sigaction *) NULL);
    (void) sigprocmask (SIG_SETMASK, &omask, (sigset_t *) NULL);
    
    /* Exec the shell.  */
    (void) execve (SHELL_PATH, (char * const *) new_argv, __environ);
    _exit (127);
  }
  else if (pid < (pid_t) 0)
    /* The fork failed.  */
    status = -1;
  else
    /* Parent side.  */
    {
      pid_t child;
      do
      {
	child = wait (&status);
	if (child <= -1 && errno != EINTR)
	{
	  status = -1;
	  break;
	}
	/* Note that pid cannot be <= -1 and therefore the loop continues
	   when wait returned with EINTR.  */
      }
      while (child != pid);
    }
  
  save = errno;
  if ((sigaction (SIGINT, &intr, (struct sigaction *) NULL) |
       sigaction (SIGQUIT, &quit, (struct sigaction *) NULL) |
       sigprocmask (SIG_SETMASK, &omask, (sigset_t *) NULL))  != 0)
  {
    if (errno == ENOSYS)
      set_errno (save);
    else
      return -1;
  }
      
  return status;
}