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#include <stdlib.h>
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#include <stdio.h>
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#include <sys/types.h>
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#include <unistd.h>
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#include <sys/wait.h>
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#define MAXFORKS	20
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#define NSYSFILE	3
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#define	tst(a,b)	(*mode == 'r'? (b) : (a))
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#define	RDR	0
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#define	WTR	1
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struct a_fork {
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	short	done;
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	short	fd;
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	int	pid;
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	int	status;
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};
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static struct a_fork the_fork[MAXFORKS];
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FILE *
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popen(char *cmd, char *mode)
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{
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	int p[2];
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	int myside, hisside, pid;
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	int i, ind;
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	for (ind = 0; ind < MAXFORKS; ind++)
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		if (the_fork[ind].pid == 0)
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			break;
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	if (ind == MAXFORKS)
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		return NULL;
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	if(pipe(p) < 0)
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		return NULL;
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	myside = tst(p[WTR], p[RDR]);
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	hisside = tst(p[RDR], p[WTR]);
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	switch (pid = fork()) {
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	case -1:
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		return NULL;
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	case 0:
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		/* myside and hisside reverse roles in child */
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		close(myside);
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		dup2(hisside, tst(0, 1));
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		for (i=NSYSFILE; i<FOPEN_MAX; i++)
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			close(i);
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		execl("/bin/ape/sh", "sh", "-c", cmd, NULL);
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		_exit(1);
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	default:
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		the_fork[ind].pid = pid;
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		the_fork[ind].fd = myside;
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		the_fork[ind].done = 0;
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		close(hisside);
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		return(fdopen(myside, mode));
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	}
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}
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int
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pclose(FILE *ptr)
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{
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	int f, r, ind;
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	int status;
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	f = fileno(ptr);
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	fclose(ptr);
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	for (ind = 0; ind < MAXFORKS; ind++)
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		if (the_fork[ind].fd == f && the_fork[ind].pid != 0)
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			break;
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	if (ind == MAXFORKS)
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		return 0;
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	if (!the_fork[ind].done) {
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		do {
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			r = wait(&status);
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			for (f = 0; f < MAXFORKS; f++)
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				if (the_fork[f].pid == r) {
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					the_fork[f].done = 1;
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					the_fork[f].status = status;
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					break;
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				}
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		} while(r != the_fork[ind].pid && r != -1);
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		the_fork[ind].status = r == -1 ? -1 : status;
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	}
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	the_fork[ind].pid = 0;
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	return (the_fork[ind].status);
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}