进程

---

更新于 2023-12-04

孤儿进程

• 父进程先于子进程结束
• 子进程被init进程接管

测试

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <errno.h>
#include <unistd.h>
#include <sys/prctl.h>

int main()
{
    int pid = fork();
    if(pid < 0) {
        printf("fail to fork\n");
        exit(0);
    }else if(pid == 0){                           //子进程
        printf("it is child %d\n", getpid());     //打印PID
        prctl(PR_SET_NAME, "test_child");         //设计进程名
        while(1){}                                //死循环
        printf("child is done!\n");
    } else {                                      //父进程
        printf("it is father %d\n", getpid());    //打印PID
        prctl(PR_SET_NAME, "test_father");        //设置进程名
        printf("father is done\n");               //结束
    }
    return 0;
}

# 下列命令查看
pstree -pt
# 进程信息如下:
# 当父进程结束后，子进程后系统init进程接管
#systemd(1)─┬─ModemManager(858)─┬─{gdbus}(879)
#           │                   └─{gmain}(874)
#           ├─test_child(1470)

僵尸进程

• 子进程结束后
• 父进程未调用wait或waitpid接受子进程结束信息
• 当父进程结束后，僵尸子进程会被系统一并回收销毁

测试

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <errno.h>
#include <unistd.h>

int main()
{
    int pid = fork();
    if(pid < 0) {
        printf("fail to fork\n");
        exit(0);
    }else if(pid == 0){                           //子进程
        printf("it is child %d\n", getpid());     //打印PID
        printf("child is done!\n");               //子进程结束
    } else {                                       //父进程
        printf("it is father %d\n", getpid());     //打印PID
        sleep(10);
        printf("father is done\n");                //父亲结束
    }
    return 0;
}

# 下列命令查看
ps aux | grep child-id
#Z+   13:27   0:00 [test_child] <defunct>