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ad787160 C |
1 | .\" Copyright (c) 1986, 1993 |
2 | .\" The Regents of the University of California. All rights reserved. | |
3 | .\" | |
c0567266 KB |
4 | .\" Redistribution and use in source and binary forms, with or without |
5 | .\" modification, are permitted provided that the following conditions | |
6 | .\" are met: | |
7 | .\" 1. Redistributions of source code must retain the above copyright | |
8 | .\" notice, this list of conditions and the following disclaimer. | |
9 | .\" 2. Redistributions in binary form must reproduce the above copyright | |
10 | .\" notice, this list of conditions and the following disclaimer in the | |
11 | .\" documentation and/or other materials provided with the distribution. | |
12 | .\" 3. All advertising materials mentioning features or use of this software | |
13 | .\" must display the following acknowledgement: | |
14 | .\" This product includes software developed by the University of | |
15 | .\" California, Berkeley and its contributors. | |
16 | .\" 4. Neither the name of the University nor the names of its contributors | |
17 | .\" may be used to endorse or promote products derived from this software | |
18 | .\" without specific prior written permission. | |
19 | .\" | |
20 | .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND | |
21 | .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
22 | .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | |
23 | .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE | |
24 | .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |
25 | .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS | |
26 | .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | |
27 | .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT | |
28 | .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY | |
29 | .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF | |
30 | .\" SUCH DAMAGE. | |
ad787160 C |
31 | .\" |
32 | .\" @(#)pipe.c 8.1 (Berkeley) 6/8/93 | |
33 | .\" | |
34 | #include <stdio.h> | |
35 | ||
36 | #define DATA "Bright star, would I were steadfast as thou art . . ." | |
37 | ||
38 | /* | |
39 | * This program creates a pipe, then forks. The child communicates to the | |
40 | * parent over the pipe. Notice that a pipe is a one-way communications | |
41 | * device. I can write to the output socket (sockets[1], the second socket | |
42 | * of the array returned by pipe()) and read from the input socket | |
43 | * (sockets[0]), but not vice versa. | |
44 | */ | |
45 | ||
46 | main() | |
47 | { | |
48 | int sockets[2], child; | |
49 | ||
50 | /* Create a pipe */ | |
51 | if (pipe(sockets) < 0) { | |
52 | perror("opening stream socket pair"); | |
53 | exit(10); | |
54 | } | |
55 | ||
56 | if ((child = fork()) == -1) | |
57 | perror("fork"); | |
58 | else if (child) { | |
59 | char buf[1024]; | |
60 | ||
61 | /* This is still the parent. It reads the child's message. */ | |
62 | close(sockets[1]); | |
63 | if (read(sockets[0], buf, 1024) < 0) | |
64 | perror("reading message"); | |
65 | printf("-->%s\en", buf); | |
66 | close(sockets[0]); | |
67 | } else { | |
68 | /* This is the child. It writes a message to its parent. */ | |
69 | close(sockets[0]); | |
70 | if (write(sockets[1], DATA, sizeof(DATA)) < 0) | |
71 | perror("writing message"); | |
72 | close(sockets[1]); | |
73 | } | |
74 | } |