使用信号来回收子进程

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

static void do_sig_child(int num)
{    
    pid_t pid;
    int status;
    while((pid = waitpid(0, &status, WNOHANG)) > 0) {
        if (WIFEXITED(status)) {
            printf("child %d exit %d\n", pid, WEXITSTATUS(status));
        }
        else if (WIFSIGNALED(status))
        {
            printf("child %d cancel signal %d\n", pid, WTERMSIG(status));
        }
    }
}


static void sys_error(const char *str)
{
    perror(str);
    exit(1);
}


int main()
{

    pid_t pid;
    int i;
    
    for (i=0; i<10; i++) {
        if((pid = fork()) == 0)
            break;
        else if (pid < 0)
            sys_error("fork");    
    }

    if (pid == 0) {
        int n = 18;
        while(n--) {
            printf("child ID: %d\n", getpid());
            sleep(1);
        }        
    }
    
    else if (pid > 0) {
        
        struct sigaction act;
        act.sa_handler = do_sig_child;
        sigemptyset(&act.sa_mask);
        act.sa_flags = 0;            
        sigaction(SIGCHLD, &act, NULL);
        
        while(1) {
            printf("Parent ID: %d\n", getpid());
            sleep(1);    
        }
    }
    
    return 0;
}