Work the Shell - Dealing with Signals   This month, I thought it
would be interesting to take a bit of a detour from my usual
multi-month programming projects and instead focus on a specific
topic that is of great importance to people writing longer
scripts: signal management.  Signals are numeric messages sent
to running applications from the operating system, other
applications or the user, and they generally invoke a specific
response like “shut down gracefully”, “stop running so I can put
you in the background” or “die!”  Most likely, you've used the
kill command to send signals to different programs, but if
you've ever pressed Ctrl-C or Ctrl-Z to stop a running app,
you've also sent signals to a running application.  A signal is
managed in a cascading manner. It's sent to the application or
script, then if the application doesn't have a specific handler
(signal management or response function), it's pushed back to
the shell or operating system. Some signals can't be managed
within individual apps, like S