/*
* DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
* Version 2, December 2004
*
* Copyright (C) 2016 Olaf Wintermann <olaf.wintermann@gmail.com>
*
* Everyone is permitted to copy and distribute verbatim or modified
* copies of this license document, and changing it is allowed as long
* as the name is changed.
*
* DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
* TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
*
* 0. You just DO WHAT THE FUCK YOU WANT TO.
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
int main(int argc, char** argv) {
int newin[2];
int newout[2];
int newerr[2];
if(pipe(newin) || pipe(newout) || pipe(newerr)) {
perror("pipe");
return EXIT_FAILURE;
}
pid_t pid = fork();
if(pid == 0) {
// child
// we need stdin, stdout and stderr refer to the previously
// created pipes
if(dup2(newin[0], STDIN_FILENO) == -1) {
perror("dup2");
return EXIT_FAILURE;
}
if(dup2(newout[1], STDOUT_FILENO) == -1) {
perror("dup2");
return EXIT_FAILURE;
}
if(dup2(newerr[1], STDERR_FILENO) == -1) {
perror("dup2");
return EXIT_FAILURE;
}
// we need to close this unused pipe
// otherwise stdin cannot reach EOF
close(newin[1]);
// execute program
return execl("/usr/bin/bc", "bc", NULL);
// end of child process
} else if(pid > 0) {
// parent
// close unused pipe endpoints
close(newout[1]);
close(newerr[1]);
// write to child
write(newin[1], "5+2\n", 4);
close(newin[1]);
// read from child
char buf[64];
ssize_t r;
while((r = read(newout[0], buf, 64)) > 0) {
write(STDOUT_FILENO, buf, r);
}
int status = -1;
waitpid(pid, &status, 0);
printf("child status code: %d\n", status);
// close all remaining pipes
close(newin[0]);
close(newout[0]);
close(newerr[0]);
} else {
// error
perror("fork");
return EXIT_FAILURE;
}
return (EXIT_SUCCESS);
}