The problem#

For certain applications it can be useful to get many quick responses from the computer, so we would like it to react to individual keypresses instead of requiring an entire command to be typed out and confirmed by pressing Enter. While this is a common feature of GUI and TUI toolkits (e.g., ncurses), it can also be useful for very lightweight inactive experiences written as simple shell scripts.

The solution#

read_keypress.sh will wait for the next keypress and return it as a string:

#!/bin/sh

STTY=$(stty --save)
stty raw -echo
SEL=$(dd if=/dev/tty bs=1k count=1 2>/dev/null)
stty "$STTY"
echo -n "$SEL"

The details#

Dice in shell#

Today I was borrowing a board game from the lending library at Emerald City Comicon and it was missing its dice. We could have gotten some physical dice somewhere, but instead we decided to use the materials we had on hand. The people I was playing with agreed that we did not want to drain our phone batteries by using a dice app on our phones, but I had a laptop with me. So I wrote a dice app for the shell:

while true
do
    reset
    seq 1 6 | shuf -n1
    seq 1 6 | shuf -n1
    read
done

This rolls two six-sided dice every time you hit enter and clears the screen before showing the result using reset.