Programs and processes, process management, foreground and background processes

One 、 Procedures and processes

Program Program： Refers to a program file , Such as notepad.exe
process Process： When a program runs , Create a in the operating system Record , Used to describe and control its operation
such as , Open multiple notepad.exe , You get multiple processes

Run multiple /usr/bin/vim, and Observe the process information
ps -ef
among , Meaning of each field ：
User： practitioners
PID： process ID
PPID： The parent process ID
STIME： Starting time
CMD： Command line invoked at startup

ps -ef | grep vi： Filter find yes vi The process of

Two 、 Process management

3、 ... and 、 Foreground and background processes

Foreground process ： Processes running in the foreground
Background processes ： Processes running in the background

Example ：
./run_tomcat run Run in front desk mode （CTRL+C End ）
./run_tomcat start Operation in background mode

difference ：

1. Is there a console
   Foreground process ： There's a console , Output to current terminal
   Background processes ： No console , No output seen
2. Whether there is a parent process
   Foreground process ：
   There are parent processes , The parent process is the current terminal
   When the terminal is turned off , The foreground process is shut down together
   Background processes ：
   The parent process is the system process （1 Process of no. ）
   When the terminal is turned off , The background process is not affected
3. force finish
   Foreground process ： Use CTRL+C force finish
   Background processes ： shiykill -9 NNN force finish