Calling fork multiple times (part 2) (With a practical example)
main.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <sys/wait.h>
#define PROCESS_NUM 10
int main(int argc, char* argv[]) {
int pids[PROCESS_NUM];
int pipes[PROCESS_NUM + 1][2];
int i;
for (i = 0; i < PROCESS_NUM + 1; i++) {
if (pipe(pipes[i]) == -1) {
printf("Error with creating pipe\n");
return 1;
}
}
for (i = 0; i < PROCESS_NUM; i++) {
pids[i] = fork();
if (pids[i] == -1) {
printf("Error with creating process\n");
return 2;
}
if (pids[i] == 0) {
// Child process
int j;
for (j = 0; j < PROCESS_NUM + 1; j++) {
if (i != j) {
close(pipes[j][0]);
}
if (i + 1 != j) {
close(pipes[j][1]);
}
}
int x;
if (read(pipes[i][0], &x, sizeof(int)) == -1) {
printf("Error at reading\n");
return 3;
}
printf("(%d) Got %d\n", i, x);
x++;
if (write(pipes[i + 1][1], &x, sizeof(int)) == -1) {
printf("Error at writing\n");
return 4;
}
printf("(%d) Sent %d\n", i, x);
close(pipes[i][0]);
close(pipes[i + 1][1]);
return 0;
}
}
// Main process
int j;
for (j = 0; j < PROCESS_NUM + 1; j++) {
if (j != PROCESS_NUM) {
close(pipes[j][0]);
}
if (j != 0) {
close(pipes[j][1]);
}
}
int y = 5;
printf("Main process sent %d\n", y);
if (write(pipes[0][1], &y, sizeof(int)) == -1) {
printf("Error at writing\n");
return 4;
}
if (read(pipes[PROCESS_NUM][0], &y, sizeof(int)) == -1) {
printf("Error at reading\n");
return 3;
}
printf("The final result is %d\n", y);
close(pipes[0][1]);
close(pipes[PROCESS_NUM][0]);
for (i = 0; i < PROCESS_NUM; i++) {
wait(NULL);
}
return 0;
}
Unix Processes in C
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