进程标识符

每一个进程有6个重要的id，分别是进程ID，父进程ID，有效用户ID，有效组ID，实际用户ID和实际组ID。

相关函数：

#include <unistd.io>

pid_t getpid();  //返回进程ID

pid_t getppid();   //返回父进程ID

pid_t getuid();   //返回用户ID

pid_t geteuid();   //返回有效用户ID

pid_t getgid();   //返回组ID

pid_t getegid();   //返回有效组ID

 

eg:

#include <stdio.h>

#include <stdlib.h>

 

int main()

{

pid_t pid,ppid,uid,euid,gid,egid;

 

pid=getpid();

ppid=getppid();

uid=getuid;

euid=geteuid();

gid=getgid();

egid=getegid();

 

printf("id of the current process: %u",pid);//pid_t实际是无符号整型

printf("parent id of the current process: %u",ppid);

printf("user id of the current process: %u",uid);

printf("effective user id of the current process: %u",euid);

printf("group id of the current process: %u",gid);

printf("effective group id of the current process: %u",egid);

 

return 0;

}