A very simple bash timer to let you know when a certain amount of time has elapsed

timer.sh

#!/bin/bash

duration="$1"

if [ -z "$duration" ]; then
	echo "Usage: $0 <duration> where duration is a number in seconds, or a number with an m or a h suffix." >&2
	echo "Examples:" >&2
	echo "$0 10" >&2
	echo "$0 15m" >&2
	exit 1
fi

numeric_duration=`echo $duration | sed 's/[^0-9]//g'`

if echo $duration | grep -q m; then
	duration_in_seconds=$(( 60 * $numeric_duration ))
elif echo $duration | grep -q h; then
	duration_in_seconds=$(( 3600 * $numeric_duration ))
else
	duration_in_seconds=$numeric_duration
fi

echo "Waiting for $duration ($duration_in_seconds seconds)..."

sleep $duration_in_seconds

echo 'Time is up!'

if which -s terminal-notifier; then
	terminal-notifier -title 'Time is up!' -message 'The timer you set has just completed.'
fi

if which -s say; then
	say 'Time is up! I repeat - time is up!'
fi