A shell I made years ago for ComputerCraft

spaapsshell.lua

path = ""
sel = 1

function init()
  term.clear()
  term.setCursorPos(1,1)

  dir = fs.list("")
  for a, i in ipairs(dir) do
    if a == 1 then
      print ("@ "..i)
    else
      print ("\t "..i)
    end
  end
   keyListener()
end

function keyListener()
  while true do
    event, code = os.pullEvent("key")
    if code == 200 then
      up()
    elseif code == 208 then
      down()
    elseif code == 14 then
      back()
    elseif code == 28 then
      forward()
	else if code == 29 then
		rmb()
    end
  end
end
end
function up()
  if sel - 1 >= 1 then
    sel = sel-1
    term.clear()
    term.setCursorPos(1, 1)
    dir = fs.list(path)
    for a, i in ipairs(dir) do
      if a == sel then
      print("@ "..i)
      else
      print("\t "..i)
      end
    end
   keyListener()
   end
end

function down()
dir = fs.list(path)
if sel + 1 <=  length(dir) then
    sel = sel + 1
    term.clear()
    term.setCursorPos(1, 1)
    for a, i in ipairs(dir) do
      if a == sel then
      print("@ "..i)
      else
      print("\t "..i)
      end
    end
   keyListener()
   end
end

function back()
	if fs.exists(fs.getDir(path)) then
		path = fs.getDir(path)
		dir = fs.list(path)
		term.clear()
		term.setCursorPos(1, 1)
  sel = 1
		for a, i in ipairs(dir) do
			if a == sel then
			print("@ "..i)
		else
			print("\t "..i)
		end
		keyListener()
	end
end
end
function forward()
	dir1 = fs.list(path)
	if fs.exists(path.."/"..dir1[sel]) then
		path = path.."/"..dir1[sel]
		if fs.isDir(path) then
			dir = fs.list(path)
			term.clear()
			term.setCursorPos(1,1)
   sel = 1
			for a,i in ipairs(dir) do
				if a == sel then
					print("@ "..i)
				else
					print("\t "..i)
				end
			end
		else
			shell.run(dir1[sel])
		end
		keyListener()
	end
end

function rmb()
	dir = fs.list(path)
	if fs.isDir(path) then
	else
	end
end
function length(t)
	b = 1
	for i, a in ipairs(t) do
		b = i
	end
	return b
end
init()