gtail

#!/usr/bin/env bash
# gtail.sh - tail a file, show growl when strings match
# uses growlnotify, the Growl command line tool: http://growl.info/documentation/growlnotify.php

#you might need to change where growlnotify lives
growl_notify="/opt/local/bin/growlnotify"

function usage() {
  echo "gtail [-f file] <regex>"
  echo "tail a file and make Growl messages for lines matching <regex>"
  echo "example: cat file.log | gtail.sh Error"
  exit
}

case $# in 
1) msg="stdin"; file="-"; re=$1 ;;
2) msg=$1; file=$1; re=$2 ;;
*) usage ;;
esac

cat $file | while read line; do
  match=$(echo "$line" | /usr/bin/sed -n /"$re"/p)
  if [ -n "$match" ]; then
    "$growl_notify"  -t "$msg"  -m "$match"  -w &
  fi
  echo $line
done