Convert UNIX timestamps to readable dates while viewing logfiles
As many admins know, logfiles are a cool thing. That is, if they are readable. Take for example the log written by Nagios.
$ grep restarting nagios.log [1423469372] Caught SIGHUP, restarting... [1423486879] Caught SIGHUP, restarting...
If you want to know the time of the restarts, you must convert the timestamps to a readable time. The Swiss-army-knife Perl and some RegEx know-how can do this easily.
$ grep restarting nagios.log | perl -pe 's/(\d+)/localtime($1)/e' [Mon Feb 9 09:09:32 2015] Caught SIGHUP, restarting... [Mon Feb 9 14:01:19 2015] Caught SIGHUP, restarting...