I recently had a need to generate a lot of Nagios host definitions. The hosts all had a similar naming convention:
foo-nnnnprjenv
Here, nnnn was a zero-padded number from 0 to 9999. In this particular environment, there were 41 hosts. A simple multiline echo command inside a while loop fed by seq produces the appropriate host stanzas we can add to our Nagios configuration. We also look up the servers IP addresses via the host command and insert those too:
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$ seq -w 1 41 | while read num; do echo "define host { use generic-host host_name foo-00${num}prjenv alias foo-00${num}prjenv address $( host foo-00${num}prjenv | awk '{print $NF}' ) register 1 } " done |
The -w option to seq causes it to output a leading-zero padded number. Redirect the output of this loop to a file, and you’ll have your Nagios host configuration. This is another reasons why having a naming convention for a large number of servers is important - it will aid you in automation and administration down the track.