How does a Linux/Unix Bash script know its own PID?
Question
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 ?
Solution
The variable '$$' contains the PID.
OTHER TIPS
use $BASHPID
or $$
See the manual for more information, including differences between the two.
TL;DRTFM
$$
Expands to the process ID of the shell.- In a
()
subshell, it expands to the process ID of the invoking shell, not the subshell.
- In a
$BASHPID
Expands to the process ID of the current Bash process.- In a
()
subshell, it expands to the process ID of the subshell
- In a
In addition to the example given in the Advanced Bash Scripting Guide referenced by Jefromi, these examples show how pipes create subshells:
$ echo $$ $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 <<< $$
11656 11656 11656
The PID is stored in $$
.
Example: kill -9 $$
will kill the shell instance it is called from.
You can use the $$
variable.
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 "$!")