CODEWITHSUNDEEP
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user2946437
user2946437

Reputation: 23

fork 3 child processes for 3 functions

I want to fork 3 child processes and have each process execute a function and busy wait until they are complete. The 3rd process is a countdown timer so once the runtime reaches 0 I will use an IPC to tell the other processes to exit. I have written the functions besides the IPC part and they run individually but I can't get fork() to create the 3 child processes to each execute a specific function. 

int main(int argc, char *argv[]) {
pid_t child_onepid, child_twopid, child_threepid, pid;

for (i = 0; i < 3; ++i) {
    pid = fork();
    if (pid) {
        continue;
    } else if (pid == 0 && i == 0) {
        show_time();
    } else if (pid == 0 && i == 1) {
        show_uptime();
    } else if (pid == 0 && i == 2) {
        show_timer(runtime);
    } else {
        printf("fork error\n");
        exit(1);
    }
}

return EXIT_SUCCESS;
}

This is my output

Time: 06/28/2014 18:55:57PM
Timer: 00:09
>Timer: 00:09
6:55pm  up 171 day(s), 10:49,  17 users,  load average: 0.34, 0.38, 0.43
6:55pm  up 171 day(s), 10:49,  17 users,  load average: 0.34, 0.38, 0.43

Upvotes: 0

Views: 662

Answers (1)

Simeon Pilgrim
Simeon Pilgrim

Reputation: 25903

Your code looks fine to me, except your error test will never hit because the if(pid) will trigger on -1.

Besides that, are you supper sure that your functions are not returning and then going around their own copy of the for loop, that would explain the output... so I added some break to make sure of that.

But I've not tested the code.

int main(int argc, char *argv[]) {
    pid_t pid;

    for (int i = 0; i < 3; ++i) {
        pid = fork();
        if (pid == -1) {
            perror("fork error\n");
            exit(EXIT_FAILURE);
        } else if (pid > 0)
            continue;
        } else if (i == 0) {
            show_time();
            break;
        } else if (i == 1) {
            show_uptime();
            break;
        } else if (i == 2) {
            show_timer(runtime);
            break;
        } 
    }

    return EXIT_SUCCESS;
}

Upvotes: 2

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