Linux Process Control

What is program, what is process, what is PID, what is PPID, what is fork, what is exec ?

process

Processes carry out tasks within the operating system. A process can be thought of as a computer program in action.

program

A program is a set of machine code(binary code) instructions and data stored in an executable image on disk and is, as such, a passive entity.

PID

process ID

PPID

process’s parent’s PID
tmux: parent process
bash: child process

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$ ps -l

F S   UID   PID   PPID   C  PRI  NI  ADDR   SZ   WCHAN  TTY      TIME CMD
0 R  1000  14945  27037  0  80   0    -    8989    -    pts/0   00:00:00 ps
0 S  1000  27037  2840   0  80   0    -    7441   wait  pts/0   00:00:00 bash

  • parent process -> child process
    1). fork a parent process
    2). exec child process