Timestamped grep-ing for log files and similar sources that provide no timestamps.

timedgrep

#!/bin/bash

# Public domain. Written by Felix Rabe in 2012.

# Timestamped grep-ing for log files and similar sources that provide no timestamps.
# Usage example (used for a Redmine 1.4 / Rails 2.3 project):
#   tail -f log/production.log | timedgrep email

look_for="$1"

while read ln ; do
  # Tried this first, didn't work: grep ... | while ... do ... done
  ( echo "$ln" | grep -q "$look_for" ) &&
    echo "$(date '+%H:%M:%S') $ln"
done