What is ps -p $$ command in Linux

The command ps -p $$ in Linux is used to display detailed information about the current shell process.

Let’s break down the command:

• ps: This stands for "process status". It's a command-line utility that provides information about the currently running processes, including their process identification numbers (PIDs).
• -p: This is an option that tells ps to select the processes with the listed PIDs. In this case, it's followed by $$, which is a special variable in bash that represents the PID of the current shell. So, $$ gets replaced by the PID of the current shell.

So, ps -p $$ will display information about the current shell process.

Here’s an example of what the output might look like:

PID TTY          TIME CMD
26344 pts/0 00:00:00 bash

In this output:

• PID is the process ID.
• TTY is the terminal type.
• TIME is the cumulative execution time.
• CMD is the command that started the process.

What is $$ Variable in Linux

The `$$` in a shell script or command line represents the Process ID (PID) of the current shell.

When you open a new terminal window, it starts a new instance of a shell. Each shell has a unique PID. The `$$` variable is a built-in variable in bash (and many other shells) that holds the PID of the current shell.

For example, if you run `echo $$` in a terminal, it will print the PID of the current shell. This is useful in scripts where you might need to know the PID of the current shell, for example, to manage subprocesses or to report the PID of a process.

A Linux Shell Script Related To $PPID Variable

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