Check the status of a NIS server on a specified host and NIS domain by asking
NIS server for "passwd.byname".
As an additional check, a username may be specified which will then be
"looked up" on the NIS server, note that this is optional and only
introduced in v1.1
Script returns OK if it gets an acceptable answer, CRITICAL if not.
This *nix script has been designed and written for the lowest common
denominator of shells (sh), uses yppoll, ypcat and grep as external