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The C programming language made simple

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Working with multiple pipes

#include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/types.h> #include <sys/wait.h> int main(int argc, char* argv[]) { int fd[3][2]; int i; for (i = 0; i < 3; i++) { if (pipe(fd[i]) < 0) { return 1; } } int pid1 = fork(); if (pid1 < 0) { return 2; } if (pid1 == 0) { // Child process 1 close(fd[0][1]); close(fd[1][0]); close(fd[2][0]); close(fd[2][1]); int x = 0; if (read(fd[0][0], &x, sizeof(int)) < 0) { return 3; } x += 5; if (write(fd[1][1], &x, sizeof(int)) < 0) { return 4; } close(fd[0][0]); close(fd[1][1]); return; } int pid2 = fork(); if (pid2 < 0) { return 5; } if (pid2 == 0) { // Child process 2 close(fd[0][0]); close(fd[0][1]); close(fd[1][1]); close(fd[2][0]); int x = 0; if (read(fd[1][0], &x, sizeof(int)) < 0) { return 6; } x += 5; if (write(fd[2][1], &x, sizeof(int)) < 0) { return 7; } close(fd[1][0]); close(fd[2][1]); return; } // Parent process close(fd[0][0]); close(fd[1][0]); close(fd[1][1]); close(fd[2][1]); int x = 0; if (write(fd[0][1], &x, sizeof(int)) < 0) { return 8; } if (read(fd[2][0], &x, sizeof(int)) < 0) { return 9; } printf("Result is %d\n", x); close(fd[0][1]); close(fd[2][0]); waitpid(pid1, NULL, 0); waitpid(pid2, NULL, 0); return 0; }