Linux非阻塞等待示例

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#define TASK_NUM 5
typedef void (*task_t)();
void download()
{
    printf("this is a download task is rnning!（正在执行下载任务）\n");
}
void printLog()
{
    printf("this is a write log task is rnning!（正在执行日志任务）\n");
}
void show()
{
    printf("this is a show info task is rnning!（正在执行显示信息任务）\n");
}
void initTasks(task_t tasks[], int num)
{
    for(int i = 0; i < num; i++) tasks[i] = NULL;
}
int addTask(task_t tasks[], task_t t)
{
    int i = 0;
    for(; i < TASK_NUM; i++)
    {
        if(tasks[i] == NULL)
        {
            tasks[i] = t;
            return 1;
        }
    }
    return 0;
}
void executeTask(task_t tasks[], int num)
{
    for(int i = 0; i < num; i++)
    {
        if(tasks[i]) tasks[i]();
    }
}
void worker(int cnt)
{
    printf("I am child, pid: %d, cnt: %d\n", getpid(), cnt);
}
int main()
{
    task_t tasks[TASK_NUM];
    initTasks(tasks, TASK_NUM);
    addTask(tasks, download);
    addTask(tasks, printLog);
    addTask(tasks, show);
    pid_t id = fork();
    if(id == 0){
        // child
        int cnt = 10;
        while(cnt)
        {
            worker(cnt);
            sleep(2);
            cnt--;
        }
        exit(0);
    }
    while(1)
    {
        //father
        int status = 0;
        // 非阻塞等待，可以让等待方在返回的时候，顺便做做自己的事情
        pid_t rid = waitpid(id, &status, WNOHANG);
        if(rid > 0)
        {
            // wait success, child quit now;
            printf("child quit success（孩子退出成功）, exit code: %d, exit signal: %d\n", (status>>8)&0xFF, status&0x7F);
            break;
        }
        else if(rid == 0)
        {
            printf("##################################################\n");
            // wait success, but child not quit
            printf("child is alive, wait again, father do other thing（孩子还活着，再次等待，父亲做其他事情）....\n");
            // 该函数内部，其实是回调式执行任务
            executeTask(tasks, TASK_NUM); // 也可以在内部进行自己移除&&新增对应的任务
            printf("##################################################\n");
        }
        else{
            // wait failed, child unknow
            printf("wait failed!\n");
            break;
        }
        sleep(1);
    }
    return 0;
}