startup.lua

function pulse(side)
    rs.setOutput(side,true)
    sleep(0.05)
    rs.setOutput(side,false)
    sleep(0.05)
end
--[[
function look()
    while true do
        local x,y = turtle.inspect()
        if x then
            if y.name == "minecraft:netherrack" then
                pulse "left"
                return
            end
        end
    end
end

function look2()
    while true do
        local x,y = turtle.inspect()
        if y.name~="minecraft:netherrack" then
            return
        end
        pulse "left"
    end
end

function mine()
    while true do
        pulse "right"
        local x,y = turtle.inspect()
        if not x or y.name=="minecraft:netherrack" then
            return
        end
    end
end

while true do
    look() look2() mine()
end]]

while true do
    local exists, data = turtle.inspect()
    if not exists then sleep(0.05)
    elseif data.name == "minecraft:netherrack" then pulse "left"
    else pulse "right" end
end