p8-16.c

SUN Solaris8平台下进程间通信

#include <signal.h>
#include <stdio.h>
#include <sys/wait.h>
#define ANYKID -1          /*  waitpid的第一个参数是 -1, 则等待任意子进程  */
#define NUMKIDS   4
static void handler(int);
volatile sig_atomic_t kids = NUMKIDS;
int main(void)
{
    int i;
    pid_t pid;
    struct sigaction act;
    sigset_t set, emptyset;
    /* 指定信号动作 */
    act.sa_handler = handler;
    sigemptyset(&act.sa_mask);
    sigaddset(&act.sa_mask, SIGCHLD);  /* 信号执行期间阻塞 SIGCHLD信号 */
    act.sa_flags = 0;
    sigaction(SIGCHLD, &act, NULL);
    sigemptyset(&emptyset);
    sigemptyset(&set);
    /* 将SIGCHLD加入至信号屏蔽 */
    sigaddset(&set, SIGCHLD);
    sigprocmask(SIG_BLOCK, &set, NULL);
    setbuf(stdout, NULL);
    for (i = 0; i < NUMKIDS; i++) {
        if (fork() == 0) {
            printf("Child %d\n", getpid());
            exit(0);
        }
    }
    while (kids > 0) 
        sigsuspend(&emptyset); /* 查看被阻塞的信号 */
}
/*
static void handler(int sig)
{
    pid_t pid;
    int status;
    pid = waitpid(ANYKID, &status, WNOHANG);
    kids--;
    printf("...child %d, now %d left\n", pid, kids);
}
*/
static void handler(int sig)
{
    pid_t pid;
    int status;
    printf("Parent (%d) in handler, ", getpid());
    pid = waitpid(ANYKID, &status, WNOHANG);
    while (pid > 0) {
        kids--;
        printf("child %d, now %d left\n", pid, kids);
        pid = waitpid(ANYKID, &status, WNOHANG);
    }
}