watchfiles: Watch multiple files and execute bash commands as file changes occur

watchfiles.md

watchfiles

• author: Thiago Andrade thiagoh@gmail.com
• license: GPLv3
• description:
• watches the given paths for changes
• and executes a given command when changes occur
• usage:
• watchfiles <paths...>

how-to-install.md

Installation

If you want to make watchfiles globally accessible on your environment execute the following instructions:

$ # clone this gist
$ git clone https://gist.github.com/5d8f53bfb64985b94e5bc8b3844dba55.git 
$ cd 5d8f53bfb64985b94e5bc8b3844dba55
$ # give execution mode
$ chmod +x watchfiles
$ # copy to some location visible by your $PATH (/usg/local/bin for example)
$ sudo cp watchfiles /usr/local/bin/watchfiles

watchfiles

#!/bin/bash
# script:  watchfiles
# author:  Thiago Andrade <thiagoh@gmail.com>
# license: GPLv3
# description:
#   watches the given paths for changes
#   and executes a given command when changes occur
# usage:
#   watchfiles <cmd> <paths...>
#

interval=1
verbose=0
quiet=0
cmd=""
error_message=""
error=0

print_error() {

  _error_message=$1
  echo "Error: ${_error_message}" 1>&2;
}

check_error() {

  if [ $error -eq 1 ]; then
    print_error "${error_message}";
    exit 1;
  fi
}

show_help() {
  echo "Usage: watchfiles [options] command [path1] [path2...]"
  echo -e "    -t --interval\t\tInterval in seconds to wait until next check"
  echo -e "    -q --quiet\t\t\tQuiet"
  echo -e "    -qq --quietquiet\t\tSuper quiet"
  echo -e "    -v --verbose\t\tVerbose (good for debug purposes)"
}

for i in "$@"; do
  key="$1"
  case $key in
      -v|--verbose)
      verbose=1
      shift
      ;;
      -q|--quiet)
      quiet=1
      shift # past argument
      ;;
      -qq|--quietquiet)
      quiet=2
      shift # past argument
      ;;
      --help)
      show_help
      shift # past argument
      exit 1;
      ;;
      -t)
      interval="$2"
      shift # past -t
      shift # past value
      ;;
      --interval=*)
      interval="${key#*=}"
      shift # past argument=value
      ;;
      *)
      cmd=$key
      shift
      break;
      ;;
  esac
done

path=$*

# echo "interval $interval"
# echo "cmd $cmd"
# echo "path $path"
# echo "verbose $verbose"
# echo
# echo

re='^[0-9]+$'
if ! [[ $interval =~ $re ]] ; then
   error_message="Interval must be an integer"
   error=1
fi

check_error

if [ -z "$path" ]; then
  error_message="No such files";
  error=1
fi

check_error

if [ $verbose -eq 1 ]; then
  quiet=0
fi

update_sha() {
  _path=$1

  current_sha=`ls -lR --time-style=full-iso $_path | sha1sum |rev| cut -d' ' -f2-| rev`
  echo $current_sha
  return 0
}

check_files() {
  tmp_path=""
  counter=0
  error_counter=0

  for file in $path; do
    if [ ! -f $file ]; then
      echo "File ${file} does not exists! Skipping it." 1>&2;
      ((error_counter=error_counter + 1))
    else
      tmp_path="$tmp_path $file"
    fi
    ((counter=counter + 1))
  done

  if [ $counter -eq $error_counter ]; then
    error=1
    error_message="No such existing or valid files"
    return 1;
  fi

  if [ $counter -eq 0 ]; then
    error=1
    error_message="At least one file is required"
    return 1;
  fi

  path=$tmp_path
}

compute_all_checksum() {

  combined_sha=""
  counter=0
  error_counter=0

  for i in $path; do
  
    file_sha=`update_sha $i`
    ret=$?
    # echo $i is $file_sha with return $ret

    if [ $ret -eq 0 ]; then
      combined_sha="${combined_sha}${file_sha}"
    else
      ((error_counter=error_counter + 1))
    fi
    ((counter=counter + 1))
  done;

  echo $combined_sha
}

check_files
check_error

files_sha=`compute_all_checksum`
previous_sha=$files_sha
execute_command() {

  if [ $verbose -eq 1 ]; then
    echo "Executing command: ${cmd}..."
  fi
  /bin/bash -c "$cmd"
}
compare() {
  files_sha=`compute_all_checksum`
  if [[ $files_sha != $previous_sha ]] ; then

    if [ $quiet -eq 0 ]; then
      echo -e "\nFile(s) changed"
    fi

    execute_command
    previous_sha=$files_sha
  else
    if [ $quiet -lt 2 ]; then
      echo -n '#'
    fi
  fi
}

trap exit SIGQUIT
trap exit SIGINT

if [ $quiet -eq 0 ]; then
  echo -e "## Watching files: ${path}"
fi

while true; do
  compare
  sleep $interval
done