Bash - detect arrow key pressed

In this short article, we would like to show how to detect any arrow key pressed in Bash.

Quick solution (input.sh file):

#!/bin/bash

while read -rsn1 input
do
    case "$input"
	in
		$'\x1B') # ESC ASCII code (https://dirask.com/posts/ASCII-Table-pJ3Y0j)
			read -rsn1 -t 0.1 input
			if [ "$input" = "[" ]
			then
				read -rsn1 -t 0.1 input
				case "$input"
				in
					A) echo '[Arrow Up]'   ;;
					B) echo '[Arrow Down]' ;;
					C) echo '[Arrow Righ]' ;;
					D) echo '[Arrow Left]' ;;
				esac
			fi
			read -rsn5 -t 0.1   # flushing stdin
			;;
		q) # q letter
			break
			;;
		*) # other letters
			echo "$input"
			;;
    esac
done

Example output (↑ → ↓ ←):

$ ./input.sh
[Arrow Up]
[Arrow Righ]
[Arrow Down]
[Arrow Left]

Reusable function

Using the below example you can reuse read_key() function in your code. The function returns arrow custom codes: [Arrow Up], [Arrow Down], [Arrow Righ], [Arrow Left] and letters.

#!/bin/bash

function read_key()
{
	if read -rsn1 input
	then
		if [ "$input" = $'\x1B' ] # ESC ASCII code (https://dirask.com/posts/ASCII-Table-pJ3Y0j)
		then
			read -rsn1 -t 0.1 input
			if [ "$input" = "[" ]
			then
				read -rsn1 -t 0.1 input
				case "$input"
				in
					A) echo '[Arrow Up]'   ;;
					B) echo '[Arrow Down]' ;;
					C) echo '[Arrow Righ]' ;;
					D) echo '[Arrow Left]' ;;
				esac
			fi
			read -rsn5 -t 0.1   # flushing stdin
		else
			echo "$input"
		fi
		return 0
	fi
	return 1
}


# Usage example:

while true
do
	input="$(read_key)"
	
	if [ "$?" -eq 0 ]
	then
		case "$input"
		in
			q) # q letter
				break
				;;
			*) # arrows + other letters
				echo "$input"
				;;
		esac
	fi
done

See also

1. Bash - interactive menu example (arrow up and down selection)