Implementation for single and multiple selects in bash

single-multiple-select.bash

function multiselect {
    # credits: https://unix.stackexchange.com/a/673436/55106 (altered with single-choice by me)
    # little helpers for terminal print control and key input
    ESC=$( printf "\033")
    cursor_blink_on()   { printf "$ESC[?25h"; }
    cursor_blink_off()  { printf "$ESC[?25l"; }
    cursor_to()         { printf "$ESC[$1;${2:-1}H"; }
    print_inactive()    { printf "$2   $1 "; }
    print_active()      { printf "$2  $ESC[7m $1 $ESC[27m"; }
    get_cursor_row()    { IFS=';' read -sdR -p $'\E[6n' ROW COL; echo ${ROW#*[}; }

    local return_value=$1
    local -n options=$2
    local -n defaults=$3
    local single_choice=$4

    local selected=()
    for ((i=0; i<${#options[@]}; i++)); do
        if [[ ${defaults[i]} = "true" ]]; then
            selected+=("true")
        else
            selected+=("false")
        fi
        printf "\n"
    done

    # determine current screen position for overwriting the options
    local lastrow=`get_cursor_row`
    local startrow=$(($lastrow - ${#options[@]}))

    # ensure cursor and input echoing back on upon a ctrl+c during read -s
    trap "cursor_blink_on; stty echo; printf '\n'; exit" 2
    cursor_blink_off

    key_input() {
        local key
        IFS= read -rsn1 key 2>/dev/null >&2
        if [[ $key = ""      ]]; then echo enter; fi;
        if [[ $key = $'\x20' ]]; then echo space; fi;
        if [[ $key = "k" ]]; then echo up; fi;
        if [[ $key = "j" ]]; then echo down; fi;
        if [[ $key = $'\x1b' ]]; then
            read -rsn2 key
            if [[ $key = [A || $key = k ]]; then echo up;    fi;
            if [[ $key = [B || $key = j ]]; then echo down;  fi;
        fi 
    }

    toggle_option() {
        local option=$1
        if [[ ${single_choice} == true ]]; then
          for ((idx=0; idx<${#options[@]}; idx++)); do
            selected[idx]=false
          done
          selected[option]=true
        else
          if [[ ${selected[option]} == true ]]; then
            selected[option]=false
          else
            selected[option]=true
          fi
        fi
    }

    print_options() {
        # print options by overwriting the last lines
        local idx=0
        local lb='['
        local rb=']'
        if [[ ${single_choice} == true ]]; then lb='('; rb=')'; fi

        for option in "${options[@]}"; do
            local prefix="$lb\e[1;31m✗\e[0m$rb"
            if [[ ${selected[idx]} == true ]]; then
              prefix="$lb\e[38;5;46m✔\e[0m$rb"
            fi

            cursor_to $(($startrow + $idx))
            if [ $idx -eq $1 ]; then
                print_active "$option" "$prefix"
            else
                print_inactive "$option" "$prefix"
            fi
            ((idx++))
        done
    }

    local active
    if [[ ${single_choice} == true ]]; then
      for ((idx=0; idx<${#options[@]}; idx++)); do
        if [[ ${selected[$idx]} == true ]]; then active=$idx; fi
      done
    else
      active=0
    fi

    while true; do
        print_options $active

        # user key control
        case `key_input` in
            space)  toggle_option $active;;
            enter)  if [[ ${single_choice} == true ]]; then toggle_option $active; fi;
                    print_options -1; break;;
            up)     ((active--));
                    if [ $active -lt 0 ]; then active=$((${#options[@]} - 1)); fi;;
            down)   ((active++));
                    if [ $active -ge ${#options[@]} ]; then active=0; fi;;
        esac
    done

    # cursor position back to normal
    cursor_to $lastrow
    printf "\n"
    cursor_blink_on

    local option
    if [[ ${single_choice} == true ]]; then
      for ((idx=0; idx<${#options[@]}; idx++)); do
        if [[ ${selected[$idx]} == true ]]; then option=${options[$idx]}; fi
      done
      eval $return_value='("${option}")'
    else
      eval $return_value='("${selected[@]}")'
    fi
}

# Usage: multiselect
# my_options=(   "Option 1"  "Option 2"  "Option 3" )
# preselection=( "true"      "true"      "false"    )
# multiselect result my_options preselection false

# Usage: soloselect
# my_options=(   "Option 1"  "Option 2"  "Option 3" )
# preselection=( "false"      "true"      "false"    )
# multiselect result my_options preselection true