Commands executed with xargs returns exit status null

Hi and thank you for writing this library!

I am developing a tool to manage long-lived java processes across a handful of servers. To kill processes, I have opted for the following solution: pgrep -f blah | xargs kill. Using your library, this command successfully kills jobs, but I encounter a runtime exception I get an exit status that is null. The backend of this software passes the exit status to the web app and so it is important to tell the user the process was successfully killed.

Any idea what is happening here? Any suggestions to avoid this problem?

Thanks again!