Linux守护进程、进程组、会话

最新推荐文章于 2022-10-11 15:42:09 发布

Raven_csdn

最新推荐文章于 2022-10-11 15:42:09 发布

阅读量408

点赞数 3

分类专栏： Linux 文章标签：守护进程进程组会话

本文链接：https://blog.youkuaiyun.com/Raven_csdn/article/details/89156632

版权

Linux 专栏收录该内容

14 篇文章

订阅专栏

本文详细介绍了Linux中的守护进程、进程组和会话。守护进程作为后台服务，独立于控制终端，不受用户登录注销影响；进程组由组长进程领导，其ID与组长相同；会话创建需注意其首进程为会话组长，创建守护进程则涉及fork、新会话创建、目录变更、文件掩码重设及文件描述符关闭等步骤。守护进程与后台进程关键区别在于是否脱离控制终端。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

1、守护进程的特点
1)、后台服务进程
2)、独立于控制终端
3)、周期性执行某任务
4)、不受用户登录注销影响（关机肯定影响）
5)、一般采用以d结尾的名字（服务）

2、进程组
1)、进程的组长

组里边的第一个进程
进程组的id==进程组的组长的id

2)、进程组组长选用规则

进程中的第一个进程

3)、进程组的id的设定

进程组的id就是组长的进程id

3、会话

1)、创建一个会话注意事项：

不能是进程组组长
创建会话的进程称为进程组的组长
有些linux版本需要root执行此操作（ubuntu不需要）
创建出的新会话会丢弃原有的控制终端
一般步骤，先fork,父亲死，儿子执行创建会话操作

2)、获取进程所属的会话id

 #include <unistd.h>
 pid_t getsid(pid_t pid);

/*(
DESCRIPTION
       getsid(0) returns the session ID of the calling process.  
       getsid(p) returns the session ID of the process with process ID p.  
       (The session ID of a process is the process group ID of the session leader.)

RETURN VALUE
       On success, a session ID is returned.  
       On error, (pid_t) -1 will be returned, and errno is set appropriately.

ERRORS
       EPERM  A process with process ID p exists, 
       but it is not in the same session as the calling process, 
       and the implementation considers this an error.

       ESRCH  No process with process ID p was found.

VERSIONS
       This system call is available on Linux since version 2.0.
*/

3)、创建一个会话

#include <unistd.h>
pid_t setsid(void);
/*
DESCRIPTION
       setsid()  creates  a  new  session if the calling process is not a process group leader.  
       The calling process is the leader of the new session (i.e., its session ID is made 
       the same as its process ID).  
       
       The calling process also  becomes the process group leader of a new process group in the session 
       (i.e., its process group ID is made the same as its process ID).

       The calling process will be the only process in the new process group and in the new session.  
       The new session has no controlling terminal.

RETURN VALUE
       On success, the (new) session ID of the calling process is returned.  
       On error, (pid_t) -1 is returned, and errno is set to indicate the error.

ERRORS
       EPERM  The process group ID of any process equals the PID of the calling process.  
       Thus, in particular, setsid() fails if the calling process is already a process group leader.
*/

在这里插入图片描述
对于进程、进程组、会话这篇文章解释的不错：
https://www.cnblogs.com/zengyiwen/p/5755191.html