I like to keep detailed logs on things, but sometimes they grow out of control. Apache’s access_log file was 8MB. I knew I was never going to need to look through the whole thing, so I wanted to shorten it. I don’t need 100,000 entries, but 500 is a good figure.

I wondered if there was some way I could do this, and how I’d go about writing a shell script to do it. But then something hit me:

tail -n 500 access_log > access_log

Use tail to print the last 500 lines, and redirect it to itself, using a single > to overwrite as opposed to append.

Of course, pay attention to one important gotcha: as I discovered when messing with the system log file, Apache does not like it when a file that it presumably keeps an open handle on randomly disappears, even if for a millisecond. The proper behavior is to stop Apache, truncate the log file, and restart it. (Something like apache2 stop && tail -n 500 access_log > access_log && apache2 start)

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