Watch file modifications with inotifywait and run arbitrary commands on those files

watchrun

#!/usr/bin/env bash

# Depends on inotifywait, from inotify-tools

# Usage: watchrun dir... -- command...
# e.g. watchrun src -- ctags -a

dirs=()
until [[ $1 == -- ]]; do
  dirs+=("$1")
  shift
done
shift
rest=("$@")

inotifywait -rme modify --format '%w%f' "${dirs[@]}" | while read -r filename; do
<&2 echo "Running for ${filename##*/}..."
"${rest[@]}" "$filename"
<&2 echo "Done."
done