Linux使用waitpid回收多个子进程的方法小结

#include <sys/wait.h>

pid_t waitpid(pid_t pid, int *status, int options);

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

int main() {
    pid_t pids[5];
    int i;
    
    // 创建5个子进程
    for (i = 0; i < 5; i++) {
        pids[i] = fork();
        if (pids[i] == 0) {
            // 子进程代码
            printf("Child process %d started\n", getpid());
            sleep(1 + rand() % 3); // 随机休眠1-3秒
            printf("Child process %d exiting\n", getpid());
            exit(0);
        }
    }
    
    // 父进程回收子进程
    int status;
    pid_t pid;
    
    for (i = 0; i < 5; i++) {
        pid = waitpid(pids[i], &status, 0);
        if (pid == -1) {
            perror("waitpid");
            exit(1);
        }
        printf("Parent reaped child %d\n", pid);
    }
    
    return 0;
}

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

int main() {
    pid_t pids[5];
    int i;
    
    // 创建5个子进程
    for (i = 0; i < 5; i++) {
        pids[i] = fork();
        if (pids[i] == 0) {
            // 子进程代码
            printf("Child process %d started\n", getpid());
            sleep(1 + rand() % 3); // 随机休眠1-3秒
            printf("Child process %d exiting\n", getpid());
            exit(0);
        }
    }
    
    // 父进程非阻塞方式回收子进程
    int status;
    pid_t pid;
    int children_left = 5;
    
    while (children_left > 0) {
        pid = waitpid(-1, &status, WNOHANG);
        
        if (pid > 0) {
            // 成功回收一个子进程
            printf("Parent reaped child %d\n", pid);
            children_left--;
        } else if (pid == 0) {
            // 有子进程仍在运行
            printf("Waiting for children to finish...\n");
            sleep(1);
        } else {
            // 出错
            perror("waitpid");
            exit(1);
        }
    }
    
    printf("All children have been reaped\n");
    return 0;
}

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

void sigchld_handler(int sig) {
    int status;
    pid_t pid;
    
    // 回收所有已终止的子进程
    while ((pid = waitpid(-1, &status, WNOHANG)) > 0) {
        printf("Parent reaped child %d\n", pid);
    }
}

int main() {
    pid_t pids[5];
    int i;
    
    // 设置SIGCHLD信号处理
    struct sigaction sa;
    sa.sa_handler = sigchld_handler;
    sigemptyset(&sa.sa_mask);
    sa.sa_flags = SA_RESTART | SA_NOCLDSTOP;
    if (sigaction(SIGCHLD, &sa, NULL) == -1) {
        perror("sigaction");
        exit(1);
    }
    
    // 创建5个子进程
    for (i = 0; i < 5; i++) {
        pids[i] = fork();
        if (pids[i] == 0) {
            // 子进程代码
            printf("Child process %d started\n", getpid());
            sleep(1 + rand() % 3); // 随机休眠1-3秒
            printf("Child process %d exiting\n", getpid());
            exit(0);
        }
    }
    
    // 父进程继续执行其他任务
    printf("Parent doing other work...\n");
    sleep(5);
    printf("Parent finished\n");
    
    return 0;
}