.\" Copyright (c) 1986 Regents of the University of California.
.\" All rights reserved.  The Berkeley software License Agreement
.\" specifies the terms and conditions for redistribution.
.\"
.\"	@(#)pipe.c	6.1 (Berkeley) 05/04/86
.\"
#include <stdio.h>

#define DATA "Bright star, would I were steadfast as thou art . . ."

/*
 * This program creates a pipe, then forks.  The child communicates to the
 * parent over the pipe. Notice that a pipe is a one-way communications
 * device.  I can write to the output socket (sockets[1], the second socket
 * of the array returned by pipe()) and read from the input socket
 * (sockets[0]), but not vice versa. 
 */

main()
{
	int             sockets[2], child;

	/* Create a pipe */
	if (pipe(sockets) < 0)
		perror("opening stream socket pair");

	if (child = fork()) {
		char            buf[1024];

		/* This is still the parent.  It reads the child's message. */
		close(sockets[1]);
		if (read(sockets[0], buf, 1024) < 0)
			perror("reading message");
		printf("-->%s\en", buf);
		close(sockets[0]);
	} else {
		/* This is the child.  It writes a message to its parent. */
		close(sockets[0]);
		if (write(sockets[1], DATA, sizeof(DATA)) < 0)
			perror("writing message");
		close(sockets[1]);
	}
}