mjhjmtu

Given a process pid, how can I

• check if the process is running a shell script?




• if yes, how can I get the child process(es) which the script is running? by pgrep -P <pid>?

Thanks.

When you execute a shell script, it will launch a process known as a subshell. As a child process of the main shell, a subshell executes a list of commands in a shell script as a batch (so-called "batch processing").

In some cases, you may want to know the process ID (PID) of the subshell where your shell script is running.

In bash, the PID of a shell script's subshell process is stored in a special variable called '$$'. This variable is read-only, and you cannot modify it in a shell script. For example:

$ cat xyz.sh
#!/bin/bash
echo "PID of this script: $$"

Which gives the following output

PID of this script: XXXX

bash shell exports several other read-only variables. For example, PPID stores the process ID of the subshell's parent process (i.e., main shell). UID stores the user ID of the current user who is executing the script. Like this(only example)

#!/bin/bash
echo "PID of this script: $$"
echo "PPID of this script: $PPID"
echo "UID of this script: $

Which gives the output

PID of this script: XXXX 
PPID of this script: XXXX 
UID of this script: XXXX