Watch a directory using bash and inotifywait

watchdir.sh

#!/bin/sh

# Usage
#
# Call the script with the directory you want to watch as an argument. e.g.:
# watchdir.sh /app/foo/
#
#
# Description:
# Uses inotifywait to look for new files in a directory and process them:
# inotifywait outputs data which is passed (piped) to a do for subcommands.
#
#
# Requirements:
# Requires inotifywait which is part of inotify-tools.
# e.g. yum install -y inotify-tools or apt-get install -y inotify-tools.
#
#
# See also:
# https://linux.die.net/man/1/inotifywait
# https://github.com/inotify-tools/inotify-tools/wiki#info
# (Might be interested in pyinotify too.)


echo "Watch $1 for file changes..."


# Be careful not to confuse the output of `inotifywait` with that of `echo`.
# e.g. missing a `\` would break the pipe and write inotifywait's output, not
# the echo's.
inotifywait \
  --monitor \
  -e close_write $1 \
  --timefmt '%Y-%m-%dT%H:%M:%S' \
  --format '%T %w %f %e' \
| while read datetime dir filename event; do
  echo "At $datetime $dir$filename changed $event"
  echo "Now, we could use $datetime $dir $filename $event and pass them to some other command, too! e.g."

  echo "python3 /app/phono.py --custom $dir$filename /tmp/$filename"
done


# --format:
#   %T  Replaced with the current Time in the format specified by the --timefmt option, which should be a format string suitable for passing to strftime(3).
#   %w  This will be replaced with the name of the Watched file on which an event occurred.
#   %f  When an event occurs within a directory, this will be replaced with the name of the File which caused the event to occur. Otherwise, this will be replaced with an empty string.
#   %e  Replaced with the Event(s) which occurred, comma-separated.
#   %Xe Replaced with the Event(s) which occurred, separated by whichever character is in the place of 'X'.


# test the script by creating a file in the watched directory, e.g.
# touch /app/foo/file1