Small utilities to draw a stopwatch as seven-segment display to the terminal. Usage: timer.sh | redraw.sh | segments.awk

redraw.sh

#!/bin/sh

esc() {
	printf '\033%s' "$@" >&2
}

clean_exit() {
	_exit_status=$?
	trap - EXIT
	# Show cursor again.
	esc '[?25h'
	exit "$_exit_status"
}; trap clean_exit EXIT TERM HUP INT

stty -echo -echonl </dev/tty

# Clear screen, store cursor position and hide cursor.
esc '[H' '[J' '7' '[?25l'

while read -r line; do
	# Restore cursor position and clear to end of screen.
	esc '8' '[J'
	printf '%s\n' "$line"
done

segments.awk

#!/usr/bin/awk -f
#
# Digital segment display.
# Usage: segments [height=<height>] [width=<width>]

function repeat(char, n,   str) {
	while (n-- > 0)
		str = str char

	return str
} 

BEGIN {
	height = 1
	width  = 2

	# Segment matrix.
	s["0_1"] = "111"; s["0_2"] = "101"; s["0_3"] = "101"
	s["0_4"] = "101"; s["0_5"] = "111"
	s["1_1"] = "001"; s["1_2"] = "001"; s["1_3"] = "001"
	s["1_4"] = "001"; s["1_5"] = "001"
	s["2_1"] = "111"; s["2_2"] = "001"; s["2_3"] = "111"
	s["2_4"] = "100"; s["2_5"] = "111"
	s["3_1"] = "111"; s["3_2"] = "001"; s["3_3"] = "111"
	s["3_4"] = "001"; s["3_5"] = "111"
	s["4_1"] = "101"; s["4_2"] = "101"; s["4_3"] = "111"
	s["4_4"] = "001"; s["4_5"] = "001"
	s["5_1"] = "111"; s["5_2"] = "100"; s["5_3"] = "111"
	s["5_4"] = "001"; s["5_5"] = "111"
	s["6_1"] = "111"; s["6_2"] = "100"; s["6_3"] = "111"
	s["6_4"] = "101"; s["6_5"] = "111"
	s["7_1"] = "111"; s["7_2"] = "001"; s["7_3"] = "001"
	s["7_4"] = "001"; s["7_5"] = "001"
	s["8_1"] = "111"; s["8_2"] = "101"; s["8_3"] = "111"
	s["8_4"] = "101"; s["8_5"] = "111"
	s["9_1"] = "111"; s["9_2"] = "101"; s["9_3"] = "111"
	s["9_4"] = "001"; s["9_5"] = "111"
	s["-_1"] = "00";  s["-_2"] = "00";  s["-_3"] = "11"
	s["-_4"] = "00";  s["-_5"] = "00"
	s[":_1"] = "0";   s[":_2"] = "1";   s[":_3"] = "0"
	s[":_4"] = "1";   s[":_5"] = "0"
	s["._1"] = "0";   s["._2"] = "0";   s["._3"] = "0"
	s["._4"] = "0";   s["._5"] = "1"
	vert_segments = 5

} NR==1 {
	on  = repeat("\xe2\x96\x88", width)
	off = repeat(" ", width)

} {
	for (line = 1; line <= vert_segments; line++) {
		str = ""
		i = 1
		while (char = substr($0, i, 1)) {
			if (i == 1)
				str = s[char "_" line]
			else
				str = str "0" s[char "_" line]

			i++
		}

		gsub(/0/, off, str)
		gsub(/1/, on, str)

		for (i = 1; i <= height; i++)
			printf "%s%s", (line==1 && i==1) ? "" : "\n", str
	}
	fflush("/dev/stdout")

} END {
	print ""
}

timer.sh

#!/bin/sh
#
# A stopwatch like timer which resets to zero when enter is pressed.

interval=1

clean_exit() {
	_exit_status=$?
	trap - EXIT
	kill "$child"
	exit "$_exit_status"
}

trap 'clean_exit' EXIT TERM HUP INT

{
	trap secs=0 USR1

	secs=0
	while :; do
		printf "%02d:%02d\n" "$((secs/60))" "$((secs%60))"
		secs=$((secs+interval))
		sleep "$interval" &
		wait
	done
} & child=$!

while read -r _; do
	kill -USR1 "$child"
done