"Unix&linux University Course" Study note seven: Process and job control

1: Process: An in-memory program + program required data + hypervisor for various status information.

2: The process is managed by the kernel, the kernel uses the scheduler, gives the process a time slice to run, and then switches to the next process.

3: Process Fork

Fork: Create a child process wait: force the process to pause, and so on another process finishes exec: Change the program that the current process executes (starts a program in the current process) exit: Terminates the current process kill: kills a process

4: Differentiate parent process or child process

The parent process calls fork to return the process ID of the child process;

The child process calls fork to return 0.

5: The source of the system process--init process

During the system boot process, the kernel manually creates an idle process #0, the idle process creates the initialization process # #, then is in an infinite loop state and does nothing, so it is not found on the process table and is not considered to exist.

While the process of the kernel of the relevant settings and the end of the boot-related operations, during this time to open the console , mount the file system , run the system initialization script , etc., process of the outstanding multi-sub-process, So become the init process.

When any child process in the system becomes an orphan process, the INIT process automatically takes over the role of the parent process to ensure that the child process ends normally.

6: Foreground process and background process

Foreground process: After startup, the shell waits for its end to run.

Background process: After startup, the process runs in the background, and the shell waits for the next command directly.

Command &: Add & After command to make the program perform as a background process

7: Process hibernation

Sleep time [s,m,h,d]

8: Job Control

9: Job suspend and resume

In the currently running job, press ^z to suspend the job and enter the FG recovery job.

Suspend and resume of 10:shell

Suspend: Suspending shell
FG: Recovery

11: Show All current jobs

Jobs

12: Resume Job (move to foreground)

FG Job

13: Move the job to the background

BG%job

14: View process information, status

Ps

15: Kill the process

Kill Pid|jobid

16: Low-priority operation

Nice command

17: Daemon

"Unix&linux University Course" Study note seven: Process and job control