Read a key from stdin in bash

readkey.sh

#!/usr/bin/env bash

# Process literal key
process_literal_key()
{
	case "$REPLY" in
		$'\E')
			ESCAPE=1
			;;
		'')
			echo 'enter'
			;;
		$'\x7F')
			echo 'back-space'
			;;
		q)
			;;
		*)
			echo "DEBUG: [$REPLY]"
			;;
	esac
}

# Process control key
process_control_key()
{
	case $REPLY in
		'[')
			;;
		*A)
			echo 'up'
			;;
		*B)
			echo 'down'
			;;
		*C)
			echo 'left'
			;;
		*D)
			echo 'right'
			;;
		*)
			process_literal_key
			;;
	esac

	ESCAPE=
}

# Read a key from stdin
read_keys()
{
	local ESCAPE=

	while read -r -s -n 1
	do
		if (( ESCAPE ))
		then
			process_control_key
		else
			process_literal_key
		fi
	done
}

if [ "${BASH_SOURCE[0]}" == "$0" ]
then
	read_keys
fi