splattael's dis dat

watchr monitors a directory tree, and triggers a user defined action whenever an observed file is modified.

Example test.watchr:

watch("lib/(.*)") { system "rake" }
Signal.trap("INT") { run_tests }

This script executes rake test whenever a file in lib/ changes.
To start watchr run watchr test.watchr on command line.

In order to execute this script itself insert a shebang and do chmod a+x test.watchr:

#!/usr/bin/env watchr
watch("lib/(.*)") { system "rake" }
Signal.trap("INT") { run_tests }

Now you execute that script with ./test.watchr.

Nice, uh? :)