進程控制函數(1)-getpgid() getpgrp() 獲取當前進程的進程組ID

定義：
pid_t getpid(void);

表頭文件：
#include<unistd.h>

說明：
getpid()用來取得目前進程的進程識別碼, 許多程序利用取到的此值來建立臨時文件, 以避免臨時文件相同帶來的問題。

返回值：
目前進程的進程識別碼

相關函數：
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\n", getpid());
        printf("child process PGID is %d\n", getpgid(0));
        printf("child process PGID is %d\n", getpgrp());
        printf("child process PGID is %d\n", getpgid(getpid()));
        exit(0);
    }
    
    sleep(3);
    printf("parent process PID is %d\n", getpid());    
    printf("parent process PGID is %d\n", getpgrp());

    return 0;
}

運行結果：

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