Watching a directory and execute command on file change

Problem

Watch a file sets or directory and run a command when anything is added, changed or deleted.

Solution

Use python watchdog module, which has a command line tool called watchmedo

    watchmedo shell-command --recursive --command 'echo ${watch_event_type}' -w -W . \
    | xargs -n 1 -I {} sh -c 'if [ "{}" = "modified" ]; then clear; make unittest; fi'

Alternatively, can use nodejs onchange module

    onchange 'app/**/*.js' 'test/**/*.js' -- npm test