Rerun a command automatically whenever files in a directory change

rerun.sh

#!/bin/bash
#
# Usage: find . -name \*.hs | rerun make
#
# Install inotifywait using 'sudo apt-get install inotify-tools' or whatever.
#
# Automatically re-run a command when a file changes.  Assumes that your
# text editor closes files after each write.  Pipe file names on standard
# input.

inotifywait --fromfile - --monitor --quiet --event close_write | \
    while read; do "$@"; done