Watching (and reacting) to changes in a directory

Watching for changes on a list of file

entr is a Linux command to watch a list of files

# Watch a list of python files and restart server on changes
find ./ -name "*.py" | entr python app.py

• Caveat : this does not react on new files.

Watching for changes and new files in existing dirs

# Watch a dir and restart server on changes and new files in existing dirs
while true
do 
    find . -name "*.py" | entr -d python ./app.py 
done

• The -d option stops makes entr exit on new files, so the list of files to watch is recomputed.
• Caveat : this does not watch new directories !