进程控制函数(1)-getpgid() getpgrp() 获取当前进程的进程组ID

定义：
pid_t getpid(void);

表头文件：
#include<unistd.h>

说明：
getpid()用来取得目前进程的进程识别码, 许多程序利用取到的此值来建立临时文件, 以避免临时文件相同带来的问题。

返回值：
目前进程的进程识别码

相关函数：
fork, kill, getpid

示例：

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

int main()
{

    pid_t pid;
    
    if ((pid = fork()) < 0) {
        perror("fork");
        exit(1);
    } else if (pid == 0) {
        printf("child process PID is %d
", getpid());
        printf("child process PGID is %d
", getpgid(0));
        printf("child process PGID is %d
", getpgrp());
        printf("child process PGID is %d
", getpgid(getpid()));
        exit(0);
    }
    
    sleep(3);
    printf("parent process PID is %d
", getpid());    
    printf("parent process PGID is %d
", getpgrp());

    return 0;
}

运行结果：

child process PID is 4471
child process PGID is 4470
child process PGID is 4470
child process PGID is 4470
parent process PID is 4470
parent process PGID is 4470