Simple monitoring script using inotify

README.md

I wanted to be able to call a simple script from the console or Neovim that would supply an executable and an arbitrary number of files.

Using inotify, each file is monitored for changes; calling the executable when one is detected. The executable is implicitly watched.

This is a very quick and dirty solution. It uses eval and doesn't perform any sanity checking. Nor does it check to see if watches are already in place. Use at your own risk.

In my own setup, I have a '~/.local/scripts/' directory which is on my $PATH. I have the script here named 'monitor'

Usage: $> monitor ./something_neat.py ./some_config.yaml ./pyproject.toml /var/tmp/something.png

This will run './something_neat.py' whenever './something_neat.py', './some_config.yaml', './pyproject.toml', or '/var/tmp/something.png' changes.

Easy install: $> curl https://gist.githubusercontent.com/koepnick/d7c16a72e065b77807d0318f4ddb72bb/raw/df7f9115858c5b82aee6606387416a111829ed49/monitor.sh -o $PATH/.local/scripts/monitor

monitor.sh

#!/bin/bash
executable=$(realpath "${1}")
targets=${@}
max_watches=$(cat /proc/sys/fs/inotify/max_user_watches)

echo "--------------------------------------------------"
echo "Targets: ${targets}"
echo "Will execute: ${executable} on change"
echo "--------------------------------------------------"
echo "The user has a maximum of ${max_watches} inotify watches"
echo "  This can be configured by adding:"
echo "     fs.inotify.max_user_watches=n"
echo "  to /etc/sysctl.conf and running"
echo "     $> sysctl --load"
echo "--------------------------------------------------"

function mon() {
    inotifywait -m \
                -e close_write \
                --include "${1}" \
                $(dirname ${1}) | 
    while read data
    do 
        eval "${executable}"
    done
}

# Iterate through all of our parameters
for i in "${@}"
do
    # Exclude the executable file. It will be the
    #  last file monitored and will not be backgrounded
    #  This is to ensure that when this script is exited,
    #  all other inotifywait instances launched from here
    #  will exit as well.
    realpath=$(realpath "${i}")
    if [[ "${realpath}" != "${executable}" ]]
    then
        mon $realpath &
    fi
done

mon $executable