1 /*
2 * DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
3 * Version 2, December 2004
4 *
5 * Copyright (C) 2016 Olaf Wintermann <olaf.wintermann@gmail.com>
6 *
7 * Everyone is permitted to copy and distribute verbatim or modified
8 * copies of this license document, and changing it is allowed as long
9 * as the name is changed.
10 *
11 * DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
12 * TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
13 *
14 * 0. You just DO WHAT THE FUCK YOU WANT TO.
15 */
16
17 #include <stdio.h>
18 #include <stdlib.h>
19 #include <unistd.h>
20 #include <sys/types.h>
21 #include <sys/wait.h>
22
23
24 int main(int argc, char** argv) {
25 int newin[2];
26 int newout[2];
27 int newerr[2];
28
29 if(pipe(newin) || pipe(newout) || pipe(newerr)) {
30 perror("pipe");
31 return EXIT_FAILURE;
32 }
33
34 pid_t pid = fork();
35 if(pid == 0) {
36 // child
37
38 // we need stdin, stdout and stderr refer to the previously
39 // created pipes
40 if(dup2(newin[0], STDIN_FILENO) == -1) {
41 perror("dup2");
42 return EXIT_FAILURE;
43 }
44 if(dup2(newout[1], STDOUT_FILENO) == -1) {
45 perror("dup2");
46 return EXIT_FAILURE;
47 }
48 if(dup2(newerr[1], STDERR_FILENO) == -1) {
49 perror("dup2");
50 return EXIT_FAILURE;
51 }
52
53 // we need to close this unused pipe
54 // otherwise stdin cannot reach EOF
55 close(newin[1]);
56
57 // execute program
58 return execl("/usr/bin/bc", "bc", NULL);
59 // end of child process
60 } else if(pid > 0) {
61 // parent
62
63 // close unused pipe endpoints
64 close(newout[1]);
65 close(newerr[1]);
66
67 // write to child
68 write(newin[1], "5+2\n", 4);
69 close(newin[1]);
70
71 // read from child
72 char buf[64];
73 ssize_t r;
74 while((r = read(newout[0], buf, 64)) > 0) {
75 write(STDOUT_FILENO, buf, r);
76 }
77
78 int status = -1;
79 waitpid(pid, &status, 0);
80 printf("child status code: %d\n", status);
81
82 // close all remaining pipes
83 close(newin[0]);
84 close(newout[0]);
85 close(newerr[0]);
86 } else {
87 // error
88 perror("fork");
89 return EXIT_FAILURE;
90 }
91
92 return (EXIT_SUCCESS);
93 }
94
95