Colorize log output with ack

Adding color to log files makes them a lot easier to understand, especially when tailing them. That’s why tools like MultiTail were created, and some logging tools can output in color. Last night I realized color could be added to any log file using ack, an awesome grep replacement that I recently found.

For example, to make 404s red in a standard Apache access log:

$ tail -f /var/log/apache2/access.log \
  | ack --passthru --color-match=red "^.* 404 .*$"

The --passthru option makes it so no lines are discarded. You can use multiple colors by piping the output through ack multiple times. The --flush option is needed to prevent pipe buffering issues and the --color option is needed to pass colors through. Here’s an example:

$ tail -f /var/log/apache2/access.log \
  | ack --flush --passthru --color --color-match=green "^.* 200 .*" \
  | ack --flush --passthru --color --color-match=yellow "^.* 302 .*" \
  | ack --flush --passthru --color --color-match=red "^.* 404 .*"

You can use more complex colors like --color="white on_red" to make errors stand out even more.

I wonder what other cool things ack can do…

Note: You could also do this with perl, but it looks a lot less maintainable.

mkscript - test script creator

I usually do something wrong when I create test scripts (typo in shebang, not executable, missing open PHP tag, etc) so I wrote a small tool called mkscript that can create them for me.

Basically, instead of doing:

$ echo '#!/usr/bin/python' > test.py
$ chmod a+x test.py

You just do:

$ mkscript test.py

It knows how to create scripts for bash, perl, php, python, and ruby based on the extension you provide. You can get it here.

Pair it with this vim function to execute the current file and you have a really quick way to create and run test scripts!

Douglas Crockford - The JSON Saga

Learned a lot from this talk.