Grup is a perl script that was originally designed to report the up status for a Group of machines. It has since mutated into a versatile tool whose flexibility rivals grep even though the names were purely coincidental.
In sprit with it's original design, grup with a single argument looks up that argument as a YP netgroup (using ypmatch) and reports whether each of the machines responds to a ping.
Without arguments, grup will tell you a little about what else it can do:
Usage: grup [-fnqs] [[-h hostname] ...] [netgroup] [-{e|r|p} commands]
-e executes an sh command for each machine with any reference of %mx
translated to the remote machine name.
-r is the same as -e with "ssh %mx" prepended
-p is the same as -e but the command is evaluated as Perl
-h specifies a hostname to use (along with/instead of) the netgroup
-f fork each command instead of running them sequentially
-n shows the first up machine that returns
-q only returns the output from the child processes
-s only returns summary information
The default command if no -e is given is:
ping -c %mx