Automatically trigger commands on source change

Sometimes, you need to write a source file and “compile” (as in “run a generic script on it”) each time you edit it, just to see the final result.

On Ubuntu, you can use the inotifywait command to keep an eye on filesystem operations.

sudo apt install inotify-tools

You can create a simple bash file such as this:

#!/bin/sh

inotifywait -m . -e modify |
while read path action file; do
    # Do something...
done

I often use it when building markdown slides.

I just create a update.sh script with the following content:

#!/bin/sh

inotifywait -m . -e modify |
while read path action file; do
    echo "[*] Generating slides..."
    pandoc -t beamer $file -V theme:metropolis -o slides.pdf
    echo "[*] Done."
done

This script will try to run pandoc on any saved file.

You just have to launch the script (./update.sh &, after making it executable – chmod +x update.sh) and then open your slides (xdg-open slides.pdf). It will update automatically every time you save your slides.md file.

Keep the generated PDF file in a separate screen for best results.