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

#!/bin/bash

​

function print_menu()  # selected_item, ...menu_items

{

    local function_arguments=($@)

​

    local selected_item="$1"

    local menu_items=(${function_arguments[@]:1})

    local menu_size="${#menu_items[@]}"

​

    for (( i = 0; i < $menu_size; ++i ))

    do

        if [ "$i" = "$selected_item" ]

        then

            echo "-> ${menu_items[i]}"

        else

            echo "   ${menu_items[i]}"

        fi

    done

}

​

function run_menu()  # selected_item, ...menu_items

{

    local function_arguments=($@)

​

    local selected_item="$1"

    local menu_items=(${function_arguments[@]:1})

    local menu_size="${#menu_items[@]}"

    local menu_limit=$((menu_size - 1))

​

    clear

    print_menu "$selected_item" "${menu_items[@]}"

    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" = "[" ]  # occurs before arrow code

                then

                    read -rsn1 -t 0.1 input

                    case "$input"

                    in

                        A)  # Up Arrow

                            if [ "$selected_item" -ge 1 ]

                            then

                                selected_item=$((selected_item - 1))

                                clear

                                print_menu "$selected_item" "${menu_items[@]}"

                            fi

                            ;;

                        B)  # Down Arrow

                            if [ "$selected_item" -lt "$menu_limit" ]

                            then

                                selected_item=$((selected_item + 1))

                                clear

                                print_menu "$selected_item" "${menu_items[@]}"

                            fi

                            ;;

                    esac

                fi

                read -rsn5 -t 0.1  # flushing stdin

                ;;

            "")  # Enter key

                return "$selected_item"

                ;;

        esac

    done

}

​

​

# Usage example:

​

selected_item=0

menu_items=('Login' 'Register' 'Guest' 'Exit')

​

run_menu "$selected_item" "${menu_items[@]}"

menu_result="$?"

​

echo

​

case "$menu_result"

in

    0)

        echo 'Login item selected'

        ;;

    1)

        echo 'Register item selected'

        ;;

    2)

        echo 'Guest item selected'

        ;;

    3)

        echo 'Exit item selected'

        ;;

esac