[C/C++][Linux] Avoiding making zombie process

If parent doesn’t use ‘wait’ system call for it’s child, that child becomes zombie after end of execution.
(At zombie state, all allocated resources are removed, but it is still in process table for parent to get child’s exit status.)
Here is very simple example

int
main (int argc, char* argv[]) {
    if (fork ()) { /* parent */
        [*A]
        sleep(999999);
    } else { /* child */
        sleep(1);
    }
    return 0;
}

In this case, child becomes zombie.
Simplest way to avoid making zombie is get exit status of child by use ‘wait’ system call at signal handler for SIGCHLD.
The point is, “DO NOT forget about getting child’s exit status not to make zombie!”
At above example following codes should be added at [*A]

int status; wait(&status);

Done!

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s