bellme

#!/bin/bash
#
# Author: gitmp01
# Version: 1.0.0
#
# Description: ring a bell when a match
# is found
#

function check_paplay_exists() {
    if [[ -z $(which paplay) ]]; then
        >&2 echo 'paplay command not found: is pulseaudio installed?'
        >&2 echo 'Install it through: '
        >&2 echo 'sudo apt get install -y pulseaudio'
        exit 1
    fi
}

function check_bell_variable() {
    if [[ -z "$BELL" ]]; then
        >&2 echo 'BELL env variable not set, set it to a sound you want to play'
        >&2 echo 'Like'
        >&2 echo 'export BELL=/usr/share/sounds/freedesktop/stereo/complete.oga'
        exit 1
    fi
}

function find_match() {
    local text=$1
    local regexp=$2
    
    local output=$(echo "$text" | grep -E "$regexp")

    if [[ -n "$output" ]]; then
        paplay "$BELL"
        echo "$output"
    fi
}

function usage() {
  local b=$(tput bold)
  local n=$(tput sgr0)
 
  echo "${b}Usage:${n} $(basename "$0") <regexp> [text]"
  echo ""
  echo "${b}Description:${n}"
  echo "   Use this script to warn you when something is printed" 
  echo "   in a log file." 
  echo ""
  echo "${b}Arguments:${n}"
  echo ""
  echo "  <regexp>    'grep -E' compatible regexp "
  echo "  text        optional text for testing the script"
  echo ""
  echo "${b}Note:${n}"
  echo "  You should set the BELL env variable to a sound like:"
  echo "    export BELL=/path/to/sound.oga"
  echo ""
  echo "  You may consider to add the line above to your .bashrc file."
  echo ""
  echo "${b}Examples:${n}"
  echo ""
  echo "  tail -f afile.log | $(basename "$0") 'Error: ¯\_(ツ)_/¯' "
  echo "  $(basename "$0") 'Hello' 'Hello World!'"
}

function show_usage_if_null() {
  local value=$1

  if [[ "$value" == "null" ]]; then
    usage
    exit 1
  fi
}

function main() {

    check_paplay_exists
    check_bell_variable

    local regex=${1:-null}
    local value=${2:-null}

    show_usage_if_null "$regex"

    # Check if file descriptor 0 is opened
    if test ! -t 0; then
      while read value; do
        find_match "$value" "$regex"
      done
    elif [[ -n "$1" ]]; then
        show_usage_if_null "$value"
        find_match "$value" "$regex"
        exit 0
    else
      usage
      exit 1
    fi
}

main "$@"