c - Why child process not getting exited before parent process calls wait() function?

Question

I'm working on c program which uses fork() and wait() calls, firstly I created five child processes and then I called wait() for five times. Whenever I execute the program it prints the same child process id in the second for loop which is displayed from the first for loop. The child processes were never getting exited before the wait() function is getting called. Why is this happening? Why the cpid is always printing the exact child process id which were displayed before?

code :

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
int main( )
{
    int child_pids[5];
    int i;
    printf("PARENT ID: %d 
", getpid());
    for(i=0;i<5;i++) {
        if(fork()==0) {
            printf("child(pid): %d of parent(pid): %d 
",getpid(),getppid());
            exit(0);
        }
    }
    for(i=0;i<5;i++) {
        int cpid=wait(NULL);
        printf("parent (pid): %d waited for child(pid): %d 
",getpid(),cpid);
    }
    return 0;
}

If there are any mistakes in my way of asking questions, please comment below

question from:https://stackoverflow.com/questions/65845325/why-child-process-not-getting-exited-before-parent-process-calls-wait-function

Answer 1

Upon exit, the child leaves an exit status that should be returned to the parent. So, when the child finishes it becomes a zombie.

Whenever the child exits or stops, the parent is sent a SIGCHLD signal. The parent can use the system call wait() or waitpid() along with the macros WIFEXITED and WEXITSTATUS with it to learn about the status of its stopped child.

If the parent exits, than you can see your children still as zombie processes (unwaited children ).

wait() just tells you which child exited so you can get the exit code. If you have more children running, then of course, others could have terminated in the meantime as well.

If you don't care about the exit status, then wait() is just fine, but you still have to wait on all children you started.