Polling adé

catch_file_changes_run_once.sh

#!/usr/bin/env bash

MONITORDIR="/tmp/test_new_files_dir/"

NOW_FILE="/tmp/catch_file_changes_now.touch"
DELAY_FILE="/tmp/catch_file_changes.touch"

AWAIT_TIME=20  # seconds
AWAIT_TIME_STR="+${AWAIT_TIME}seconds"
CMD="echo \"da command\""

echo "[start] $(date)"

await_and_run () {
	echo "  [${1}] waiting ${AWAIT_TIME} + 1 seconds inside await function... (eventually running your command)"
	sleep ${AWAIT_TIME}
	sleep 1  # ensure it's really newer
	touch ${NOW_FILE}
	if [[ ${NOW_FILE} -nt ${DELAY_FILE}  ]]
	then
		echo "  [${1}] awaiting succeeded (no new files added during ${AWAIT_TIME} seconds), will run command > ${CMD} <"
		eval "${CMD}"
	else
		echo "  [${1}] awaing aborted, as newer file was added, will not run command yet..."
	fi
}

# -m: Instead of exiting after receiving a single event, execute indefinitely.
# -r: Watch all subdirectories of any directories passed as arguments.  Watches will be set up recursively to an unlimited depth.  Symbolic links are not traversed.  Newly created  subdirectories will also be watched.
# -e: Event type, we use create:  A file or directory was created within a watched directory.
inotifywait -m -r -e create --format '%w%f' "${MONITORDIR}" | while read NEWFILE
do
	echo "File ${NEWFILE} has been created beneath watched folder ${MONITORDIR}"
	touch -d"+20seconds" ${DELAY_FILE}
	# run function in background to not block detection of newer files coming in
	await_and_run ${NEWFILE} &
	echo "do loop end of inotifywait, waiting for next newfile..."
done

# cleanup
rm -vf "${NOW_FILE}"
rm -vf "${DELAY_FILE}"

echo "[done] $(date)"

Sample run:

[start] Wed 03 Aug 2022 02:06:36 PM CEST
Setting up watches.  Beware: since -r was given, this may take a while!
Watches established.
File /tmp/test_new_files_dir/yesef1 has been created beneath watched folder /tmp/test_new_files_dir/
do loop end of inotifywait, waiting for next newfile...
  [/tmp/test_new_files_dir/yesef1] waiting 20 + 1 seconds inside await function... (eventually running your command)
File /tmp/test_new_files_dir/yesef2 has been created beneath watched folder /tmp/test_new_files_dir/
do loop end of inotifywait, waiting for next newfile...
  [/tmp/test_new_files_dir/yesef2] waiting 20 + 1 seconds inside await function... (eventually running your command)
File /tmp/test_new_files_dir/yesef3 has been created beneath watched folder /tmp/test_new_files_dir/
do loop end of inotifywait, waiting for next newfile...
  [/tmp/test_new_files_dir/yesef3] waiting 20 + 1 seconds inside await function... (eventually running your command)
  [/tmp/test_new_files_dir/yesef1] awaing aborted, as newer file was added, will not run command yet...
  [/tmp/test_new_files_dir/yesef2] awaing aborted, as newer file was added, will not run command yet...
  [/tmp/test_new_files_dir/yesef3] awaiting succeeded (no new files added during 20 seconds), will run command > echo "da command" <
da command```