Simple shell countdown

countdown.sh

#! /bin/sh

if [ -z "$1" ]; then
	echo "Missing argument!  Usage:"
	echo -e "\t$0 <time string>"
	exit 1
fi

TARGET=$(date -d"$1" "+%s")
TOGO=$((TARGET-$(date "+%s")))
CLEARLINE='\r\033[2K'
BOLD='\033[1m'
NORMAL='\033[0m'

if [ ${TOGO} -le 0 ]; then
	echo "Target time not in the future; difference is ${TOGO} seconds."
	exit 2
fi

# Years to go?
PERIOD=$((365*24*60*60))
while [ ${TOGO} -gt ${PERIOD} ]; do
	printf "${CLEARLINE}$(date "+%Y-%m-%dT%H:%M:%S%Z: ") T minus ${BOLD}%i${NORMAL} years, ${BOLD}%02i${NORMAL} days, ${BOLD}%02i${NORMAL} hours, ${BOLD}%02i${NORMAL} minutes, ${BOLD}%02i${NORMAL} seconds" \
		$((TOGO/PERIOD)) \
		$(($((TOGO%PERIOD))/$((PERIOD/365)))) \
		$(($((TOGO%$((PERIOD/365))))/$((PERIOD/365/24)))) \
		$(($((TOGO%$((PERIOD/365/24))))/$((PERIOD/365/24/60)))) \
		$((TOGO%$((PERIOD/365/24/60))))
	if [ $((TOGO%PERIOD)) -gt 0 ]; then
		sleep $((TOGO%PERIOD))
	else
		if [ $((TOGO/PERIOD)) -gt 10 ]; then
			if [ $((TOGO%$((10*PERIOD)))) -gt 0 ]; then
				sleep $((TOGO%$((10*PERIOD))))
			else
				sleep $((10*PERIOD))
			fi
		else
			sleep ${PERIOD}
		fi
	fi
	TOGO=$((TARGET-$(date "+%s")))
done

# Days to go?
PERIOD=$((PERIOD/365))
while [ ${TOGO} -gt ${PERIOD} ]; do
	printf "${CLEARLINE}$(date "+%Y-%m-%dT%H:%M:%S%Z: ") T minus ${BOLD}%02i${NORMAL} days, ${BOLD}%02i${NORMAL} hours, ${BOLD}%02i${NORMAL} minutes, ${BOLD}%02i${NORMAL} seconds" \
		$((TOGO/PERIOD)) \
		$(($((TOGO%$((PERIOD))))/$((PERIOD/24)))) \
		$(($((TOGO%$((PERIOD/24))))/$((PERIOD/24/60)))) \
		$((TOGO%$((PERIOD/24/60))))
	if [ $((TOGO%PERIOD)) -gt 0 ]; then
		sleep $((TOGO%PERIOD))
	else
		if [ $((TOGO/PERIOD)) -gt 10 ]; then
			if [ $((TOGO/PERIOD)) -gt 100 ]; then
				if [ $((TOGO%$((100*PERIOD)))) -gt 0 ]; then
					sleep $((TOGO%$((100*PERIOD))))
				else
					sleep $((100*PERIOD))
				fi
			else
				if [ $((TOGO%$((10*PERIOD)))) -gt 0 ]; then
					sleep $((TOGO%$((10*PERIOD))))
				else
					sleep $((10*PERIOD))
				fi
			fi
		else
			sleep ${PERIOD}
		fi
	fi
	TOGO=$((TARGET-$(date "+%s")))
done

# Hours to go?
PERIOD=$((PERIOD/24))
while [ ${TOGO} -gt ${PERIOD} ]; do
	printf "${CLEARLINE}$(date "+%Y-%m-%dT%H:%M:%S%Z: ") T minus ${BOLD}%02i${NORMAL} hours, ${BOLD}%02i${NORMAL} minutes, ${BOLD}%02i${NORMAL} seconds" \
		$((TOGO/PERIOD)) \
		$(($((TOGO%$((PERIOD))))/$((PERIOD/60)))) \
		$((TOGO%$((PERIOD/60))))
	if [ $((TOGO%PERIOD)) -gt 0 ]; then
		sleep $((TOGO%PERIOD))
	else
		if [ $((TOGO/PERIOD)) -gt 10 ]; then
			if [ $((TOGO%$((10*PERIOD)))) -gt 0 ]; then
				sleep $((TOGO%$((10*PERIOD))))
			else
				sleep $((10*PERIOD))
			fi
		else
			sleep ${PERIOD}
		fi
	fi
	TOGO=$((TARGET-$(date "+%s")))
done

# Minutes to go?
PERIOD=$((PERIOD/60))
while [ ${TOGO} -gt ${PERIOD} ]; do
	printf "${CLEARLINE}$(date "+%Y-%m-%dT%H:%M:%S%Z: ") T minus ${BOLD}%02i${NORMAL} minutes, ${BOLD}%02i${NORMAL} seconds" \
		$((TOGO/PERIOD)) \
		$((TOGO%$((PERIOD))))
	if [ $((TOGO%PERIOD)) -gt 0 ]; then
		sleep $((TOGO%PERIOD))
	else
		if [ $((TOGO/PERIOD)) -gt 10 ]; then
			if [ $((TOGO%$((10*PERIOD)))) -gt 0 ]; then
				sleep $((TOGO%$((10*PERIOD))))
			else
				sleep $((10*PERIOD))
			fi
		else
			sleep ${PERIOD}
		fi
	fi
	TOGO=$((TARGET-$(date "+%s")))
done

# Seconds to go?
PERIOD=$((PERIOD/60))
while [ ${TOGO} -ge ${PERIOD} ]; do
	printf "${CLEARLINE}$(date "+%Y-%m-%dT%H:%M:%S%Z: ") T minus ${BOLD}%02i${NORMAL} seconds" \
		${TOGO}
	if [ $((TOGO/PERIOD)) -gt 10 ]; then
		if [ $((TOGO%$((10*PERIOD)))) -gt 0 ]; then
			sleep $((TOGO%$((10*PERIOD))))
		else
			sleep $((10*PERIOD))
		fi
	else
		sleep ${PERIOD}
	fi
	TOGO=$((TARGET-$(date "+%s")))
done

echo -e "${CLEARLINE}$(date "+%Y-%m-%dT%H:%M:%S%Z: ") ${BOLD}T reached${NORMAL}!"