watch is a linux bash script to monitor file modification recursively and execute bash commands as changes occur

watch.sh

#!/usr/bin/env bash
# script:  watch
# authors:  Mike Smullin <mike@smullindesign.com>, Santiago de Pedro <santiago.pedro23@gmail.com>
# license: GPLv3
# description:
#   watches the given path for changes
#   and executes a given command when changes occur
# usage:
#   watch <path> <cmd...>
#

path=$1

if [[ ! $path ]] ; then
    path=`pwd`
fi

shift
cmd=$*

if [[ ! $cmd ]] ; then
    cmd="NONE"
fi

sha=0
update_sha() {
  sha=`ls -lR --time-style=full-iso $path | sha1sum`
}
update_sha
previous_sha=$sha
build() {
  if [[ $cmd != "NONE" ]] ; then
      echo -en "--> building...\n\n"
      $cmd
  fi
}

compare() {
  update_sha
  if [[ $sha != $previous_sha ]] ; then
    echo -en "\n--> change DETECTED\n"
    build
    previous_sha=$sha
  else
    echo -n .
  fi
}
trap build SIGINT
trap exit SIGQUIT

echo -e  "--> Press Ctrl+C to force build, Ctrl+\\ to exit."
echo -e  "--> command [$cmd]"
echo -e  "--> watching [$path]"
while true; do
  compare
  sleep 1
done