What does $$ do

Voyager7 · 01-21-2011, 07:21 AM

hi,
What does $$ do?
it gives back a number but what is it?
Also what are these $?, $$ called?
Having a tough time googling them, so their generic name would help

Thnx

sycamorex · 01-21-2011, 07:34 AM

Here you go:
http://tldp.org/LDP/abs/html/interna...s.html#PROCCID

HTH

Soji Antony · 01-21-2011, 09:51 AM

$$ is the PID( Process id) of the current process.
For example

Code:

echo $$

gives pid of current shell.

Hope this helps

Soji Antony · 01-21-2011, 10:00 AM

Code:

man bash

will give you a detailed explanation

Code:

Special Parameters
?      Expands to the exit status of the most recently executed foreground pipeline.
$      Expands  to  the  process  ID of the shell.  In a () subshell, it expands to the process ID of the current shell, not the subshell.