How to write a bash script that will listen for changes in a file?

Question

bash

I know that there are all sorts of task runners, but I want to do this, I wrote a bash script

#!/bin/bash

sass -t compressed build/sass/app.scss:public/css/app.css
autoprefixer-cli  -b "> 0%"  public/css/app.css -o public/css/app.css
cleancss -o public/css/app.css public/css/app.css

It executes 3 commands, but it turns out that I have to run
$ sh sass.config.sh every time
. I would like it to work as a watch, but for this it must listen for changes in the app.scss file.
How can I do this?
Or at least tell me how webpack can run this shell script after it has compiled its js (at least webpack works in watch mode there)

Answer 1

while true; do
    inotifywait -qq -e create,close_write,modify,move,delete $CHECK_FOLDER && $BUILD_COMMAND
done