11638Srgrimes.\" Copyright (c) 1986, 1993 21638Srgrimes.\" The Regents of the University of California. All rights reserved. 31638Srgrimes.\" 41638Srgrimes.\" Redistribution and use in source and binary forms, with or without 51638Srgrimes.\" modification, are permitted provided that the following conditions 61638Srgrimes.\" are met: 71638Srgrimes.\" 1. Redistributions of source code must retain the above copyright 81638Srgrimes.\" notice, this list of conditions and the following disclaimer. 91638Srgrimes.\" 2. Redistributions in binary form must reproduce the above copyright 101638Srgrimes.\" notice, this list of conditions and the following disclaimer in the 111638Srgrimes.\" documentation and/or other materials provided with the distribution. 121638Srgrimes.\" 3. All advertising materials mentioning features or use of this software 131638Srgrimes.\" must display the following acknowledgement: 141638Srgrimes.\" This product includes software developed by the University of 151638Srgrimes.\" California, Berkeley and its contributors. 161638Srgrimes.\" 4. Neither the name of the University nor the names of its contributors 171638Srgrimes.\" may be used to endorse or promote products derived from this software 181638Srgrimes.\" without specific prior written permission. 191638Srgrimes.\" 201638Srgrimes.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 211638Srgrimes.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 221638Srgrimes.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 231638Srgrimes.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 241638Srgrimes.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 251638Srgrimes.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 261638Srgrimes.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 271638Srgrimes.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 281638Srgrimes.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 291638Srgrimes.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 301638Srgrimes.\" SUCH DAMAGE. 311638Srgrimes.\" 321638Srgrimes.\" @(#)pipe.c 8.1 (Berkeley) 6/8/93 331638Srgrimes.\" 341638Srgrimes#include <stdio.h> 351638Srgrimes 361638Srgrimes#define DATA "Bright star, would I were steadfast as thou art . . ." 371638Srgrimes 381638Srgrimes/* 391638Srgrimes * This program creates a pipe, then forks. The child communicates to the 401638Srgrimes * parent over the pipe. Notice that a pipe is a one-way communications 411638Srgrimes * device. I can write to the output socket (sockets[1], the second socket 421638Srgrimes * of the array returned by pipe()) and read from the input socket 438875Srgrimes * (sockets[0]), but not vice versa. 441638Srgrimes */ 451638Srgrimes 461638Srgrimesmain() 471638Srgrimes{ 481638Srgrimes int sockets[2], child; 491638Srgrimes 501638Srgrimes /* Create a pipe */ 511638Srgrimes if (pipe(sockets) < 0) { 521638Srgrimes perror("opening stream socket pair"); 531638Srgrimes exit(10); 541638Srgrimes } 551638Srgrimes 561638Srgrimes if ((child = fork()) == -1) 571638Srgrimes perror("fork"); 581638Srgrimes else if (child) { 591638Srgrimes char buf[1024]; 601638Srgrimes 611638Srgrimes /* This is still the parent. It reads the child's message. */ 621638Srgrimes close(sockets[1]); 631638Srgrimes if (read(sockets[0], buf, 1024) < 0) 641638Srgrimes perror("reading message"); 651638Srgrimes printf("-->%s\en", buf); 661638Srgrimes close(sockets[0]); 671638Srgrimes } else { 681638Srgrimes /* This is the child. It writes a message to its parent. */ 691638Srgrimes close(sockets[0]); 701638Srgrimes if (write(sockets[1], DATA, sizeof(DATA)) < 0) 711638Srgrimes perror("writing message"); 721638Srgrimes close(sockets[1]); 731638Srgrimes } 741638Srgrimes} 75