I have a script in Bash called Script.sh that needs to know its own PID. In other words, I need to get PID inside Script.sh.
Any idea how to do this?
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7 Answers
The variable $$ contains the PID.
answered Mar 22, 2010 at 15:53
1 Comment
Murtaza Haji
How can i get the pid from outside the script , i use
top but it shows a lot of random processesuse $BASHPID or $$
See the [manual][1] for more information, including differences between the two.
TL;DRTFM
$$Expands to the process ID of the shell.- In a
()subshell, it expands to the process ID of the invoking shell, not the subshell.
- In a
$BASHPIDExpands to the process ID of the current Bash process (new to bash 4).- In a
()subshell, it expands to the process ID of the subshell [1]: http://www.gnu.org/software/bash/manual/bashref.html#Bash-Variables
- In a
answered Mar 22, 2010 at 15:53
Comments
In addition to the example given in the Advanced Bash Scripting Guide referenced by Jefromi, these examples show how pipes create subshells:
$ echo $$ $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 <<< $$
11656 11656 11656
answered Mar 22, 2010 at 17:55
2 Comments
Sopalajo de Arrierez
could you please explain what does "<<<" mean? Thanks.
Dennis Williamson
It redirects a string into the loop (or anything that reads
stdin). The string is referred to as a "here string".The PID is stored in $$.
Example: kill -9 $$ will kill the shell instance it is called from.
2 Comments
willeM_ Van Onsem
kill -9 (with -9 flag) is considered to be harmful and only to be used if it is absolutely necessary).
Bruno Bronosky
It's considered "dangerous" because the process does not get a chance to respond to the signal (and possibly clean up after itself). Doing
kill -9 $$ does exactly 1 thing. It kills the current shell process. This is useful if you have done something in the shell session that you do not want written to .bash_history Like: docker run -e PASSWORD=hunter2 ircbotYou can use the $$ variable.
answered Mar 22, 2010 at 15:54
Comments
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.
Comments
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 "$!")
