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From: mcafee@umich.edu (Sean McAfee)
Newsgroups: comp.sys.apple2.gno
Subject: Re: Why no popen()?  Could this be the reason?
Date: 22 Jan 1996 14:36:17 GMT
Organization: University of Michigan
Lines: 107
Message-ID: <4e07d1$s34@lastactionhero.rs.itd.umich.edu>
References: <4dq5d4$m9u@lastactionhero.rs.itd.umich.edu> <4durq7$1b0@apollo.csd.net>
NNTP-Posting-Host: verne.ifs.umich.edu

In article <4durq7$1b0@apollo.csd.net>,
Jawaid Bazyar <bazyar@hypermall.com> wrote:
>  Without seeing the code for your popen, I couldn't guess what the problem
>is.

Well, OK.  I was just wondering if there was a reason popen() isn't around,
since it's rather conspicuous by its absence.

Here's my code.  It's VERY crude, but I just wanted a quick-fix to get
gnuplot compiled.


#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <sys/wait.h>
#include <gno/gno.h>

static int fd[2];
static int openfd;
static char *myargv[20];
static char *combuf;

static struct flist {
	FILE *stream;
	int pid;
	struct flist *next;
} *listp, *head = NULL, *tail = NULL;

FILE *popen(const char *command, const char *mode)
{
	FILE *stream;
	int i, j, pid, done = 0, myargc = 1;
	char c, *cp;
	void doit(void);

	if (mode[1] || mode[0]!='r' && mode[0]!='w')
		return NULL;

	openfd = mode[0]=='w';		/* openfd is the end of the pipe
					   the parent should keep open  */
	i = strpos(command, ' ');
	combuf = malloc(i+1);
	strncpy(combuf, command, i);	/* this code puts the command name
	combuf[i] = '\0';		   into combuf[] and myargv[0]  */
	myargv[0] = malloc(i+1);
	strncpy(myargv[0], command, i);
	myargv[0][i] = '\0';

	j = i+1;
	do {
		i = strpos(command+j, ' ');
		if (i==-1) {
			i = strlen(command+j);
			done = 1;
		}
		cp = malloc(i+1);	/* This loop parses the words */
		strncpy(cp, command+j, i);  /* in the command line into */
		cp[i] = '\0';			/* the myargv[] array  */
		myargv[myargc++] = cp;
		j += i+1;
	} while (!done);
	myargv[myargc] = NULL;

	pipe(fd);
	pid = fork(doit);
	close(fd[1-openfd]);
	stream = fdopen(fd[openfd], mode);

	listp = malloc(sizeof(struct flist));	/* Put the stream and pid */
	listp->stream = stream;			/* a list for later       */
	listp->pid = pid;			/* retrieval by pclose()  */
	listp->next = NULL;

	if (head) {
		tail->next = listp;
		tail = listp;
	} else
		head = tail = listp;

	return stream;
}


int pclose(FILE *stream)
{
	union wait waitbuf;

	fclose(stream);
	for (listp=head; listp && listp->stream == stream; listp=listp->next)
		;
	if (!listp)
		return -1;
	wait(&waitbuf);
	return waitbuf.w_status;
}


static void doit(void)
{
	dup2(fd[1-openfd], fileno(openfd ? stdin : stdout));
	close(fd[0]);
	close(fd[1]);
	execvp(combuf, myargv);
}