#!/bin/bash

die()
{
    echo "Error: $*" >&2
    exit 1
}

show_default()
{
    d=$(lpstat -d)
    case "$d" in
        'system default destination: '*) echo "${d##* }" ;;
    esac

}

set_default()
{
    (
        set -x
        lpoptions -d "$1"
    )
}

printers()
{
    lpstat -p | while read line
    do
        case "$line" in
            "printer "*)
                p="${line#printer }"
                echo "${p%% *}"
                set -- "$p" "$line"
                ;;
        esac
    done
}

show_printers_with_default()
{
    default_printer=$(show_default) # can be empty
    for p
    do
        if [ "$p" = "$default_printer" ]
        then
            echo "[default] $p"
        else
            echo "          $p"
        fi
    done | nl
}

set -e
set -- $(printers)

echo
show_printers_with_default "$@"
echo

read -p 'Choose default printer> ' i || die "Error reading input"
[ "$i" ] || exit 0
[ "$i" -gt 0 ] || die "Invalid choice: $i"
choice=${!i} && [ "$choice" ] || die "Invalid choice: $i"

set_default $choice