Child not Responding

Question

Hello I'm having issues with sending signals from the father process to the child process. The Child doesn't respond to the signed sent by the father process:

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

int main()
{
pid_t pid;
pid = fork();

if(pid > 0) {
printf("Hello, my son!\n");
    sleep(5); /* Sleep for 5 seconds... */
    kill(pid, SIGUSR1);
    printf("Goodbye, son!\n");
    }
else {
    printf("Son is running\n");
    pause(); /* Wait for some signal... */
    printf("I received the signal!");
    }
}

The son doesn't received the signal it only says it's running here is the output: output

Answer 1

The default behavior when SIGUSR1 is received is termination, so the child never prints the message. To handle the signal, you can use sigaction:

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

void handle(int sig, siginfo_t *i, void *v) { return; }

int
main(void)
{
        pid_t pid = fork();

        if( pid > 0 ){
                printf("Hello, my child!\n");
                sleep(1); /* Sleep for 1 second. */
                kill(pid, SIGUSR1);
                printf("Goodbye, child!\n");
        } else {
                struct sigaction act;
                memset(&act, 0, sizeof act);
                act.sa_sigaction = handle;

                if( sigaction( SIGUSR1, &act, NULL ) ){
                        perror("sigaction");
                        exit(1);
                }

                printf("Child is running\n");
                pause(); /* Wait for some signal... */
                printf("I received the signal!\n");
        }
}