[SOLVED] What does mean $$ or $! in bash?

Issue

It's kind of easy question but I didn't find any information. What does mean $! or $$ in bash?

For example: ps -p $! or pstree $$?

Solution

Actually, these variables were inherited by bash from the Bourne shell.

$$ means current PID.

$! is the PID of the last program your shell ran in the background (e.g. myprog &)

Here is a list of shell variables:

• http://unixhelp.ed.ac.uk/scrpt/scrpt2.2.2.html

Answered By - paulsm4

Answer Checked By - David Marino (WPSolving Volunteer)