How to set up output to certain specifications - lua

Question

I figured out the main concept of my code which reads in a file and sets it to a key then reads in another file and displays the info based on that file. How do I add line 1, line 2. line 3 and so on in front of the output? As well as add ------------ above and below each new line.
-- see if the file exists
function file_exists(file)
local f = io.open("data.txt", "rb")
if f then f:close() end
return f ~= nil
end
-- get all lines from a file, returns an empty
-- list/table if the file does not exist
function lines_from(file)
if not file_exists(file) then return {} end
lines = {}
for line in io.lines("data.txt") do
first_word = string.match(line, "%a+") -- word
lines[first_word] = line
lines[#lines + 1] = lin
end
return lines
end
local lines = lines_from(file)
function key_file(file)
if not file_exists(file) then return {} end
keys = {}
for line in io.lines("keys.txt") do
key = string.match(line, "%a+")
table.insert(keys, key)
end
return keys
end
local lines = lines_from("data.txt")
local keys = key_file("keys.txt")
for _, key in ipairs(keys) do
print(lines[key])
end

Answer 1

I'll answer this in a more general way as your code is not working atm.
You can simply add print commands in the for loop that prints the lines. Or you alter the texts by in some way. See Lua reference documentation for string manipulation and concat operator ..
local numLine = 0
for _, key in pairs(keys) do
numLine = numLine + 1
print("Line " .. numLine .. ": " .. lines[key])
print("----------")
end