$$ in a script vs $$ in a subshell
bash, scripting, shell
Solution
I tried and escaping (to pass the $$ to the subshell) does not work as the subshell inherits the $$ value from the parent bash. The solution to this is to use $BASHPID.
(echo $$; echo $BASHPID)
prints the PID from the parent shell and from the subshell.
Problem
`$$` gives process id of the script process when used in a script, like this: Example 1 ``` #!/bin/bash # processid.sh # print process ids ps -o cmd,pid,ppid echo "The value of \$\$ is $$" $ ./processid.sh CMD PID PPID bash 15073 4657 /bin/bash ./processid.sh 15326 15073 ps -o cmd,pid,ppid 15327 15326 The value of $$ is 15326 ``` Observe the pid given by `$$` and `ps` is 15326 My shell prompt is pid 15073 But in a subshell, `$$` gives pid of parent shell (which is 15073) Example 2 ``` $ ( ps -o cmd,pid,ppid ; echo $$ ) CMD PID PPID bash 15073 4657 bash 15340 15073 ps -o cmd,pid,ppid 15341 15340 15073 ``` Here subshell is pid 15340 Question: Why so? Isn't the script also running in a subshell? What's the difference between the subshell in example 2 and the shell in which the script runs in example 1?