[App] billboard.lua

local termMod = require("/terminal")
local Terminal = termMod.new()
local Monitor = termMod.new()

local msgLocation = "/OS/temp/displayScreenMessage.txt"
function Main()
    local p = peripheral.find("monitor")
    Monitor:setOutput(p)
    updateDisplay(false)
    term.setCursorBlink(false)
    Terminal:reset()
    while true do
        print("Displaying message to the screen.")
        print()
        local menu = {
            "Edit",
            "Update",
            "Auto Update",
            "Preview",
            "Clear",
            "Exit"
        }
        local menuName, menuIndex = Terminal:promptOptions("What would you like to do?",false,menu)
        if menuIndex == 1 then ---------------------- edit
            shell.run("edit "..msgLocation)
        elseif menuIndex == 2 then ------------------ update
            updateDisplay(true)
        elseif menuIndex == 3 then ------------------ auto update
            while true do
                updateDisplay(false)
                Terminal:reset()
                print("Updating every 5 seconds, terminate to stop.")
                os.sleep(5)
            end
        elseif menuIndex == 4 then ------------------ preview
            Terminal:reset()
            local lines = getMsg()
            for i = 1, #lines do
                Terminal:writeLine(i,lines[i])
            end
            term.setCursorPos(1,Terminal.size.y-1)
            Terminal:pressAnyKeyToContinue()
        elseif menuIndex == 5 then ------------------ clear
            Monitor:reset()
        elseif menuIndex == #menu then --exit
            return
        end
    end
end

function getMsg()
    if fs.exists(msgLocation) == false then return {} end
    local file_lines = {} --#create a blank table
    local file = fs.open( msgLocation, "r" ) --#open the file in read mode
    for line in file.readLine do --#file.readLine is a function which acts similar to pairs or ipairs, and therefor can be used like this
        file_lines[ #file_lines + 1 ] = line --#set file_lines[ the number of items in file_lines + 1 ] equal to the current line
    end
    print("Got message of "..#file_lines.." lines...")
    return file_lines
end

function updateDisplay(doPrint)
    if Monitor == nil then
        Terminal:reset()
        print("Cant find a monitor.")
        print(p)
        os.sleep(1.5)
    else
        Monitor:reset()
        local lines = getMsg()
        if #lines == 0 then
            print("\nGo to 'Edit' and create a message first!")
            os.sleep(1)
        else
            for i = 1, #lines do
                Monitor:writeLine(i,lines[i])
            end
            Terminal:reset()
            if doPrint then
                print("Display updated!")
                os.sleep(0.75)
            end
        end
    end
end


Main()