Shell script that watches HTML templates and compiles with Handlebars - bash

Question

I'm trying to create a script that watches my HTML template files in a directory and when it notify's changes, it compiles the template. I can't get it working, this is what I got:
#!/bin/sh
while FILENAME=$(inotifywait --format %w -r templates/*.html)
do
COMPILED_FILE=$(echo "$FILENAME" | sed s/templates/templates\\/compiled/g | sed s/.html/.js/g)
handlebars $FILENAME -f $COMPILED_FILE -a
done
I use inotifywait to watch the current dir, although I want it also to check for sub directories. The compiled files then need to be saved in a sub directory called templates/compiled with optionally the sub directory.
So templates/foo.html needs to be compiled and stored as templates/compiled/foo.js
So templates/other/foo.html needs to be compiled and stored as templates/compiled/other/foo.js
As you can see I tried to watch the directoy and replace the templates/ name with templates/compiled.
Any help is welcome!

Answer 1

A few observations, then a solution:
Passing the argument -r templates/*.html only matches .html files in templates/ — not in templates/other/. Instead we're going to do -r templates which notifies us of changes to any file anywhere under templates.
If you don't use inotifywait in --monitor mode, you will miss any files that are changed in the brief period that handlebars is running (which could happen if you save all your open files at once). Better to do something like this:
#!/bin/bash
watched_dir="templates"
while read -r dirname events filename; do
printf 'File modified: %s\n' "$dirname$filename"
done < <(inotifywait --monitor --event CLOSE_WRITE --recursive "$watched_dir")
Then, as for transforming the paths, you could do something like:
$ dirname=templates/other/
$ echo "${dirname#*/}"
other/
$ echo "$watched_dir/compiled/${dirname#*/}"
templates/compiled/other/
$ filename=foo.html
$ echo "${filename%.html}"
foo
$ echo "${filename%.html}.js"
foo.js
$ echo "$watched_dir/compiled/${dirname#*/}${filename%.html}.js"
templates/compiled/other/foo.js
Notice that we can leverage Bash's builtin parameter expansion — no need for sed.
Putting it all together, we get:
#!/bin/bash
watched_dir="templates"
while read -r dirname events filename; do
[[ "${filename##*.}" != 'html' ]] && continue
output_path="$watched_dir/compiled/${dirname#*/}${filename%.html}.js"
handlebars "$dirname$filename" -f "$output_path" -a
done < <(inotifywait --monitor --event CLOSE_WRITE --recursive "$watched_dir")