/****************************************************************************
 * Nagios run command utilities
 *
 * License: GPL
 * Copyright (c) 2005 nagios-plugins team
 *
 * $Id: utils_cmd.c 1434 2006-06-18 19:36:48Z opensides $
 *
 * Description :
 *
 * A simple interface to executing programs from other programs, using an
 * optimized and safe popen()-like implementation. It is considered safe
 * in that no shell needs to be spawned and the environment passed to the
 * execve()'d program is essentially empty.
 *
 *
 * The code in this file is a derivative of popen.c which in turn was taken
 * from "Advanced Programming for the Unix Environment" by W. Richard Stevens.
 *
 * Care has been taken to make sure the functions are async-safe. The one
 * function which isn't is cmd_init() which it doesn't make sense to
 * call twice anyway, so the api as a whole should be considered async-safe.
 *
 * License Information:
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#define NAGIOSPLUG_API_C 1

/** includes **/
#include "common.h"
#include "utils_cmd.h"
#include "utils_base.h"

#ifdef HAVE_SYS_WAIT_H
# include <sys/wait.h>
#endif

/** macros **/
#ifndef WEXITSTATUS
# define WEXITSTATUS(stat_val) ((unsigned)(stat_val) >> 8)
#endif

#ifndef WIFEXITED
# define WIFEXITED(stat_val) (((stat_val) & 255) == 0)
#endif

/* 4.3BSD Reno <signal.h> doesn't define SIG_ERR */
#if defined(SIG_IGN) && !defined(SIG_ERR)
# define SIG_ERR ((Sigfunc *)-1)
#endif

/* This variable must be global, since there's no way the caller
 * can forcibly slay a dead or ungainly running program otherwise.
 * Multithreading apps and plugins can initialize it (via CMD_INIT)
 * in an async safe manner PRIOR to calling cmd_run() or cmd_run_array()
 * for the first time.
 *
 * The check for initialized values is atomic and can
 * occur in any number of threads simultaneously. */
static pid_t *_cmd_pids = NULL;

/* Try sysconf(_SC_OPEN_MAX) first, as it can be higher than OPEN_MAX.
 * If that fails and the macro isn't defined, we fall back to an educated
 * guess. There's no guarantee that our guess is adequate and the program
 * will die with SIGSEGV if it isn't and the upper boundary is breached. */
#ifdef _SC_OPEN_MAX
static long maxfd = 0;
#elif defined(OPEN_MAX)
# define maxfd OPEN_MAX
#else	/* sysconf macro unavailable, so guess (may be wildly inaccurate) */
# define maxfd 256
#endif


/** prototypes **/
static int _cmd_open (char *const *, int *, int *)
	__attribute__ ((__nonnull__ (1, 2, 3)));

static int _cmd_fetch_output (int, output *, int)
	__attribute__ ((__nonnull__ (2)));

static int _cmd_close (int);

/* prototype imported from utils.h */
extern void die (int, const char *, ...)
	__attribute__ ((__noreturn__, __format__ (__printf__, 2, 3)));