Each Linux command returns an exit code, with 0 indicating success and non-zero values indicating failure. You can use the $? variable to access the exit code and control program flow in scripts. Be ...

There are quite a few exit codes used on Linux systems, though no listing you can display when you’re feeling curious. In fact, you won’t see the numeric codes unless you specifically ask for them.

Knowing how to work with and display exit codes on the Linux command line or in scripts can help make errors more obvious. Exit codes on the Linux command line are numeric values that provide feedback ...

If you have a process ID but aren't sure whether it's valid, you can use the most unlikely of candidates to test it: the kill command. If you don't see any reference to this on the kill(1) man page, ...