Parent process versus child process

A parent process is a process that has started one or more child processes. A perfect example will be your terminal and your bash shell; when you open your terminal, your bash shell is started as well.

To get the PID of a process, you can use the pgrep command followed by the process name:

pgrep process_name

For example, to get the PID of your terminal process, you can run:

elliot@ubuntu-linux:~$ pgrep terminal 
10009

The PID of my terminal is 10009. Now, let's get the PID of the bash process:

elliot@ubuntu-linux:~$ pgrep bash 
10093

The PID of my bash shell is 10093. Now, you can get the information of your bash process by using the -p option followed by the bash PID:

elliot@ubuntu-linux:~$ ps -fp 10093
UID     PID   PPID  C  STIME  TTY   TIME   CMD
elliot 10093 10009  0  13:37 pts/1 00:00:00 bash

You can see from the output that the PPID of my bash process is equal to the PID of my terminal process. This proves that the terminal process has started...