Watch a directory for changes and run a command when it does

watchdir

#!/bin/bash
# STOP! Before going any further, think: are you going to regret the decision
# to write this script?
#     Deciding to write this in bash was not one of my better decisions.
#     -- https://twitter.com/alex_gaynor/status/369892494114164736

IFS="`printf "\n\t"`"
set -u

if [[ "$#" -lt 2 ]]; then
    echo "USAGE: $0 DIR CMD [... ARGS]"
    exit 1
fi

dir="$1"
shift

if [[ ! -e "$dir" ]]; then
    echo "ERROR: $dir does not exist!"
    exit 1
fi

while :; do
    "${@}"
    res="$?"
    if [[ "$?" -ne 0 ]]; then
        echo "Command exited with: $res"
    fi
    sleep 1
    changed="$(fswatch -E --exclude '\.sw.$' -1 "$dir")"
    res="$?"
    echo "$changed"
    if [[ "$res" -ne 0 || -z "$changed" ]]; then
        exit 1
    fi
    echo "$changed"
done