A polling based script to watch a directory and execute a command if something change.

watcher.sh

#!/bin/bash

# A polling based script to watch a directory and execute a command if something change.
# Reference: https://www.baeldung.com/linux/command-execute-file-dir-change
# Example: ./watcher.sh ~/Documents "echo 'Detected the modification of a file or directory'" 

DIR_TO_WATCH=${1}
COMMAND=${2}
 
trap "echo Exited!; exit;" SIGINT SIGTERM
while [[ 1=1 ]]
do
  watch --chgexit -n 1 "ls --all -l --recursive --full-time ${DIR_TO_WATCH} | sha256sum" && ${COMMAND}
  sleep 1
done