Nagios installations which rely on working external commands should have a check which verifys that external commands are really working. This plugins sends a test command and checks the logfile if that command occurs.
The plugin uses the File::Tail module from cpan.
$ check_external_commands -t 120 -p /usr/local/nagios/var/rw/nagios.cmd \
-l /usr/local/nagios/var/nagios.log
WARNING - command took 23s|command_write=0.85s command_read=22s