popen.c

<B>Digital的Unix操作系统VAX 4.2源码</B>

#ifndef lint
static	char	*sccsid = "@(#)popen.c	4.1	(ULTRIX)	7/3/90";
#endif lint

/************************************************************************
 *									*
 *			Copyright (c) 1985 by				*
 *		Digital Equipment Corporation, Maynard, MA		*
 *			All rights reserved.				*
 *									*
 *   This software is furnished under a license and may be used and	*
 *   copied  only  in accordance with the terms of such license and	*
 *   with the  inclusion  of  the  above  copyright  notice.   This	*
 *   software  or  any  other copies thereof may not be provided or	*
 *   otherwise made available to any other person.  No title to and	*
 *   ownership of the software is hereby transferred.			*
 *									*
 *   This software is  derived  from  software  received  from  the	*
 *   University    of   California,   Berkeley,   and   from   Bell	*
 *   Laboratories.  Use, duplication, or disclosure is  subject  to	*
 *   restrictions  under  license  agreements  with  University  of	*
 *   California and with AT&T.						*
 *									*
 *   The information in this software is subject to change  without	*
 *   notice  and should not be construed as a commitment by Digital	*
 *   Equipment Corporation.						*
 *									*
 *   Digital assumes no responsibility for the use  or  reliability	*
 *   of its software on equipment which is not supplied by Digital.	*
 *									*
 ************************************************************************/
/************************************************************************
 *			Modification History
 *
 *	David L Ballenger, 5-Sep-1985
 * 001	Allocate array of PIDs dynamically based on number on the number
 *	of files which can be opened.
 *
 *	Based on:  popen.c	4.4 (Berkeley) 9/25/83
 *
 ************************************************************************/

#include <stdio.h>
#include <signal.h>
#define	tst(a,b)	(*mode == 'r'? (b) : (a))
#define	RDR	0
#define	WTR	1

extern	char	*calloc();
extern	int	getdtablesize();

static	int	*popen_pid;

FILE *
popen(cmd,mode)
char	*cmd;
char	*mode;
{
	int p[2];
	register myside, hisside, pid;

	/* Allocate the array to store the PIDs for popen()'d pipes.
	 * The array is allocated dynamically to allow programs to move
	 * to systems with a larger file descriptor tables without
	 * being recompiled.
	 */
	if (popen_pid == NULL) {
		popen_pid = (int *)calloc(getdtablesize(),sizeof(int));
		if (popen_pid == NULL)
			return(NULL);
	}

	if(pipe(p) < 0)
		return NULL;
	myside = tst(p[WTR], p[RDR]);
	hisside = tst(p[RDR], p[WTR]);
	if((pid = fork()) == 0) {
		/* myside and hisside reverse roles in child */
		close(myside);
		if (hisside != tst(0, 1)) {
			dup2(hisside, tst(0, 1));
			close(hisside);
		}
		execl("/bin/sh", "sh", "-c", cmd, 0);
		_exit(1);
	}
	if(pid == -1) {
		close(myside);
		close(hisside);
		return NULL;
	}
	popen_pid[myside] = pid;
	close(hisside);
	return(fdopen(myside, mode));
}

pclose(ptr)
FILE *ptr;
{
	register int f, r;
	void (*hstat)(), (*istat)(), (*qstat)();
	int status;

	f = fileno(ptr);
	fclose(ptr);

	/* If the pid array has not been allocated, then this wasn't
	 * opened with popen(), so return the error status.
	 */
	if (popen_pid == NULL)
		return(-1);

	istat = signal(SIGINT, SIG_IGN);
	qstat = signal(SIGQUIT, SIG_IGN);
	hstat = signal(SIGHUP, SIG_IGN);
	while((r = wait(&status)) != popen_pid[f] && r != -1)
		;
	if(r == -1)
		status = -1;

	signal(SIGINT, istat);
	signal(SIGQUIT, qstat);
	signal(SIGHUP, hstat);
	return(status);
}