when-changed: Run a command when a file is changed

What is it?

Tired of switching to the shell to test the changes you just made to
your code? Starting to feel like a mindless drone, manually running
pdflatex for the 30th time to see how your resume now looks?

Worry not, when-changed is here to help! Whenever it sees that you have
changed the file, when-changed runs any command you specify.

So to generate your latex resume automatically, you can do this:

$ when-changed CV.tex pdflatex CV.tex

Sweetness!

What do I need?

Python 3.6+
watchdog

Installation

pipx install https://github.com/eviweb/when-changed/archive/master.zip

Usage

when-changed [OPTION] FILE COMMAND...
when-changed [OPTION] FILE [FILE ...] -c COMMAND

FILE can be a directory. Use %f to pass the filename to the command.

Options:

-r Watch recursively
-v Verbose output. Multiple -v options increase the verbosity. The maximum is 3: -vvv.
-1 Don't re-run command if files changed while command was running
-s Run command immediately at start
-q Run command quietly
-k Kill the running command before restarting it (useful for long-running processes)
-d DELAY Debounce: wait DELAY seconds before running, coalescing rapid changes into a single run
-p PATTERN Only react to files matching PATTERN (glob, e.g. *.py). Can be repeated for multiple patterns.

Environment variables

when-changed provides the following environment variables:

WHEN_CHANGED_EVENT: reflects the current event type that occurs. Could be either:
- file_created
- file_modified
- file_moved
- file_deleted
WHEN_CHANGED_FILE: provides the full path of the file that has generated the event.

Examples

Restart a server when source files change, killing the previous instance:

$ when-changed -k -r src/ python server.py

Debounce rapid changes (e.g. formatter touching many files at once):

$ when-changed -d 0.5 -r src/ make test

Watch only Python and YAML files in a directory:

$ when-changed -r -p '*.py' -p '*.yml' src/ make lint

eviweb/when-changed