4.1.1. Handling Signals

Signals other that SIG_KILL and SIG_STOP may be caught and execute a defined signal handler function.

#include <stdio.h>
#include <signal.h>

static void sig_handler(int);

int main ()
{
    int i, parent_pid, child_pid, status;

    if(signal(SIGUSR1, sig_handler) == SIG_ERR)
        printf("Parent: Unable to create handler for SIGUSR1\n");
    if(signal(SIGUSR2, sig_handler) == SIG_ERR)
        printf("Parent: Unable to create handler for SIGUSR2\n");
    parent_pid = getpid();

    if((child_pid = fork()) == 0) {
        kill(parent_pid, SIGUSR1);
        for (;;) pause();
    }
    else {
        kill(child_pid, SIGUSR2);
        sleep(3);
        printf("Parent: Terminating child ...\n");
        kill(child_pid, SIGTERM);
        wait(&status);
        printf("done\n");
    }
}

static void sig_handler(int signo) {
    switch(signo) {
        case SIGUSR1:  /* Incoming SIGUSR1 */
            printf("Parent: Received SIGUSER1\n");
            break;
        case SIGUSR2:  /* Incoming SIGUSR2 */
            printf("Child: Received SIGUSER2\n");
            break;
        default: break;
    }
    return;
}