Linux SIGCHLD信号

#include
#include
#include
#include
#include
#include
#include
#include

void Myfun(int num) {
    printf("捕捉到的信号%d\n", num);
    while(1) {
        int ret = waitpid(-1, NULL, WNOHANG);
        if(ret > 0) {
            printf("child die, pid = %d\n", ret);
        } else if(ret == 0) {
            break;
        }
    }
}


int main() {
    sigset_t set;
    sigemptyset(&set);
    sigaddset(&set, SIGCHLD);
    sigprocmask(SIG_BLOCK, &set, NULL);

    pid_t pid;
    for(int i = 0; i < 20; i++) {
        pid = fork();
        if(pid == 0) {
            break;
        }    
    }
    if(pid > 0) {
        struct sigaction act;
        act.sa_flags = 0;
        act.sa_handler = Myfun;
        sigemptyset(&act.sa_mask);

        sigaction(SIGCHLD, &act, NULL);

        sigprocmask(SIG_UNBLOCK, &set, NULL);

        while(1) {
            printf("parent process pid%d\n", getpid());
            sleep(2);
        }
    } else if(pid == 0) {
        printf("child process pid:%d\n", getpid());
    }

    return 0;
}