1 | /* Creating a Pipe |
2 | Copyright (C) 1991-2022 Free Software Foundation, Inc. |
3 | |
4 | This program is free software; you can redistribute it and/or |
5 | modify it under the terms of the GNU General Public License |
6 | as published by the Free Software Foundation; either version 2 |
7 | of the License, or (at your option) any later version. |
8 | |
9 | This program is distributed in the hope that it will be useful, |
10 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
11 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
12 | GNU General Public License for more details. |
13 | |
14 | You should have received a copy of the GNU General Public License |
15 | along with this program; if not, see <https://www.gnu.org/licenses/>. |
16 | */ |
17 | |
18 | #include <sys/types.h> |
19 | #include <unistd.h> |
20 | #include <stdio.h> |
21 | #include <stdlib.h> |
22 | |
23 | /* Read characters from the pipe and echo them to @code{stdout}. */ |
24 | |
25 | void |
26 | read_from_pipe (int file) |
27 | { |
28 | FILE *stream; |
29 | int c; |
30 | stream = fdopen (file, "r" ); |
31 | while ((c = fgetc (stream: stream)) != EOF) |
32 | putchar (c: c); |
33 | fclose (stream); |
34 | } |
35 | |
36 | /* Write some random text to the pipe. */ |
37 | |
38 | void |
39 | write_to_pipe (int file) |
40 | { |
41 | FILE *stream; |
42 | stream = fdopen (file, "w" ); |
43 | fprintf (stream, "hello, world!\n" ); |
44 | fprintf (stream, "goodbye, world!\n" ); |
45 | fclose (stream); |
46 | } |
47 | |
48 | int |
49 | main (void) |
50 | { |
51 | pid_t pid; |
52 | int mypipe[2]; |
53 | |
54 | /*@group*/ |
55 | /* Create the pipe. */ |
56 | if (pipe (pipedes: mypipe)) |
57 | { |
58 | fprintf (stderr, "Pipe failed.\n" ); |
59 | return EXIT_FAILURE; |
60 | } |
61 | /*@end group*/ |
62 | |
63 | /* Create the child process. */ |
64 | pid = fork (); |
65 | if (pid == (pid_t) 0) |
66 | { |
67 | /* This is the child process. |
68 | Close other end first. */ |
69 | close (fd: mypipe[1]); |
70 | read_from_pipe (file: mypipe[0]); |
71 | return EXIT_SUCCESS; |
72 | } |
73 | else if (pid < (pid_t) 0) |
74 | { |
75 | /* The fork failed. */ |
76 | fprintf (stderr, "Fork failed.\n" ); |
77 | return EXIT_FAILURE; |
78 | } |
79 | else |
80 | { |
81 | /* This is the parent process. |
82 | Close other end first. */ |
83 | close (fd: mypipe[0]); |
84 | write_to_pipe (file: mypipe[1]); |
85 | return EXIT_SUCCESS; |
86 | } |
87 | } |
88 | |