How does a Linux/Unix Bash script know its own PID?
BashScriptingPidBash Problem Overview
I have a script in Bash called Script.sh, and it needs to know its own PID (i.e. I need to get PID inside the Script.sh )
Any idea how to do this ?
Bash Solutions
Solution 1 - Bash
The variable $$ contains the PID.
Solution 2 - Bash
use $BASHPID or $$
See the [manual][1] for more information, including differences between the two.
TL;DRTFM
$$Expands to the process ID of the shell.- In a
()subshell, it expands to the process ID of the invoking shell, not the subshell.
- In a
$BASHPIDExpands to the process ID of the current Bash process (new to bash 4).- In a
()subshell, it expands to the process ID of the subshell [1]: http://www.gnu.org/software/bash/manual/bashref.html#Bash-Variables
- In a
Solution 3 - Bash
In addition to the example given in the Advanced Bash Scripting Guide referenced by Jefromi, these examples show how pipes create subshells:
$ echo $$ $BASHPID | cat -
11656 31528
$ echo $$ $BASHPID
11656 11656
$ echo $$ | while read line; do echo $line $$ $BASHPID; done
11656 11656 31497
$ while read line; do echo $line $$ $BASHPID; done <<< $$
11656 11656 11656
Solution 4 - Bash
The PID is stored in $$.
Example: kill -9 $$ will kill the shell instance it is called from.
Solution 5 - Bash
You can use the $$ variable.
Solution 6 - Bash
If the process is a child process and $BASHPID is not set, it is possible to query the ppid of a created child process of the running process. It might be a bit ugly, but it works. Example:
sleep 1 &
mypid=$(ps -o ppid= -p "$!")
Solution 7 - Bash
Wherever you are (on an interactive command line or in a script), and in the case you do NOT have access to $BASHPID, you can get access to your current shell pid with this :
bash -c 'echo $PPID'
where simple quotes are essential to prevent premature string interpretation (so as to be sure the interpretation occurs in the child process, not in the current one). The principle is just to create a child process and ask for its parent pid, that is to say "myself". This code is simpler than ps-based Joakim solution.