1994-05-30 19:09:18 +00:00
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.\" Copyright (c) 1986, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)pipe.c 8.1 (Berkeley) 6/8/93
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.\"
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#include <stdio.h>
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#define DATA "Bright star, would I were steadfast as thou art . . ."
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/*
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* This program creates a pipe, then forks. The child communicates to the
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* parent over the pipe. Notice that a pipe is a one-way communications
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* device. I can write to the output socket (sockets[1], the second socket
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* of the array returned by pipe()) and read from the input socket
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1995-05-30 06:58:14 +00:00
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* (sockets[0]), but not vice versa.
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1994-05-30 19:09:18 +00:00
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*/
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main()
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{
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int sockets[2], child;
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/* Create a pipe */
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if (pipe(sockets) < 0) {
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perror("opening stream socket pair");
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exit(10);
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}
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if ((child = fork()) == -1)
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perror("fork");
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else if (child) {
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char buf[1024];
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/* This is still the parent. It reads the child's message. */
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close(sockets[1]);
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if (read(sockets[0], buf, 1024) < 0)
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perror("reading message");
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printf("-->%s\en", buf);
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close(sockets[0]);
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} else {
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/* This is the child. It writes a message to its parent. */
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close(sockets[0]);
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if (write(sockets[1], DATA, sizeof(DATA)) < 0)
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perror("writing message");
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close(sockets[1]);
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}
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}
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