/* @(#)popen.c	4.5 (Berkeley) 07/06/84 */

#include <stdio.h>
#include <signal.h>

#define	tst(a,b)	(*mode == 'r'? (b) : (a))
#define	RDR	0
#define	WTR	1

static	int popen_pid[20];

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

	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;
{
	int child, pid, status, omask;

	child = popen_pid[fileno(ptr)];
	fclose(ptr);
#define	mask(s)	(1 << ((s)-1))
	omask = sigblock(mask(SIGINT)|mask(SIGQUIT)|mask(SIGHUP));
	while ((pid = wait(&status)) != child && pid != -1)
		;
	(void) sigsetmask(omask);
	return (pid == -1 ? -1 : status);
}