CODEWITHSUNDEEP
coperating-systemsignalsmultiple-processes
thyago stall
thyago stall

Reputation: 1704

Sleep function has not effect when handling SIGCHLD

What is the relation between the SIGCHLD handling and the sleep function?

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <signal.h>
#include <string.h>
#include <sys/types.h>
#include <sys/wait.h>

sig_atomic_t child_exit_status;

void clean_up_child_process(int signal_number)
{
    int status;
    wait(&status);
    child_exit_status = status;
}

int main()
{
    struct sigaction sigchld_action;
    memset(&sigchld_action, 0, sizeof(sigchld_action));
    sigchld_action.sa_handler = &clean_up_child_process;
    sigaction(SIGCHLD, &sigchld_action, NULL);

    pid_t child_pid = fork();
    if (child_pid > 0) {
        printf("Parent process, normal execution\n");
        sleep(60);
        printf("After sleep\n");
    } else {
        printf("Child\n");
    }

    return 0;
}

Because when I execute the code from above, it prints:

Parent process, normal execution
Child
After sleep

But there is no effect from the sleep function in the execution. Is there any particularity that happens here?

Upvotes: 0

Views: 275

Answers (1)

thyago stall
thyago stall

Reputation: 1704

From the documentation:

RETURN VALUE

Zero if the requested time has elapsed, or the number of seconds left to sleep, if the call was interrupted by a signal handler.

What happens is that the sleep function is interrupted by the signal handler. So checking the return value of it a 60 is seen. Another strategy could be used to sleep the remaining seconds if that's the intention.

Upvotes: 1

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