Making the CLI Application

In this chapter, we'll write the CLI logic, starting with a simple echo, then the "hello" detector we planned from the start.

Creating the Skeleton

Let's add some simple boilerplate using argparse. This program will print back anything we pass as arguments back into the console:

src/main.lua

local argparse = require("argparse")

-- Create an argument parser
local parser = argparse("script", "An example.")
parser:argument("input", "Input file.")

local args = parser:parse()

-- Directly print out the "input" argument
print(args.input)

lx run executes our project's entrypoint, the file we configured in the [run] section of lux.toml, and passes any arguments along to it. Run the following to see your code in action:

lx run "Testing our code!"

You should see Testing our code! printed right back at you in the console!

Expanding the Code

Now we'll add the feature we set out to build: checking whether the input contains "hello". Let's expand our code to do just that:

src/main.lua

--- Checks whether input has the word "hello"
--- @param input string
local function has_hello(input)
    return input:lower():find("hello") ~= nil
end

local argparse = require("argparse")

-- Create an argument parser
local parser = argparse("script", "An example.")
parser:argument("input", "Input file.")

local args = parser:parse()

-- Directly print out the "input" argument
if has_hello(args.input) then
    print("Your input has the word 'hello' in it!")
else
    print("Your input does not have the word 'hello' in it!")
end

Below are some example outputs, feel free to play around with the input:

lx run "Hello, world!"

Your input has the word 'hello' in it!

lx run "Hi, world!"

Your input does not have the word 'hello' in it!

Well done! Our code is ready. Next up: testing.