The challenge is to author a Command Line Interface(CLI) tool for Node.js. Start at level 1 and progress as far as you can with in the time limit. We will be building a CLI tool to parse log files.
At the end will collectively compare solutions and the designs made behind them.
Hello World
Begin by setting up your package by running npm init. Then we can create our first script index.js and add a hello world with an interpreter directive(it will be the first line).
#! /usr/bin/env node
console.log('Hello World')
Go ahead and test this by running. `node index.js
Once we have our script setup the next step is to make it available on our machine. Now there are a few ways this can be acheived. Ultimately what we need to do is ensure our script is executable and available in our system $PATH variable. Fortunately for use we can use npm to make this very easy.
Start by telling npm the name of your script using the bin property of our package.json
"bin": {
"cli-challenge": "./index.js"
},
Then use the npm link command. After running this command you can see it created a symlink to our global npm module folder which is already available on our $PATH.
You should now be able to run cli-challenge in your terminal and see the results of your "hello world".
Input/Output
The command line uses stdin(Standard In), stdout(Standard Out), and stderr(Standard Error). These interfaces allow us to read and write to the command line.
Luckily for us Node.js exposes these via the process and implements them as Streams. It also provides the readline package which provides an interface for reading from Streams.
Let's update our script to use this package.
const readline = require('readline');
const rl = readline.createInterface({
input: process.stdin,
output: process.stdout
});
rl.question('What do you think of Node.js? ', (answer) => {
// TODO: Log the answer in a database
console.log(`Thank you for your valuable feedback: ${answer}`);
rl.close();
});
Now test your script again.
Command Line Options
Now let's get down to it! At this point the solutions are going to be up to you and will probably require some research.
Since we are building a log parsing cli tool we will need an option for our tool to tell us where our logs are located. This level you need to add the file parameter to your script. How you choose to accomplish this is up to you, there is more than one way. You will also find an access_log.zip file in the repository. This contains a large file of apache access logs taken from here.
The test to pass this level is you should be able to run this command.
cli-challenge --file=/path/to/access.log
And recieve the line count.
Hint: Like mentioned with the readline package you are dealing with Streams. If you need a crash course on Streams, Substacks' Stream Handbook is a great resource.
Bonus points: add a --help option which shows you the available options and commands with explanations of how to use them.
Progress Bar
Now if we have a very large log file this could take awhile. So let's add some communication to our users of our parsing progress. This level you need to add a progress bar that displays on the command line while parsing takes place.
Filter to find and return all 404 records.
Color Ouput
Exactly that! Color your output. Maybe make 404's red and 200's green!
Date Range
Allow your script to accept a date range with a start and end argument. And only return log lines between then. The timeformat is left to you.
The test to pass this level is you should be able to run this command.
cli-challenge --file=/path/to/access.log --start=00:00:12 02-16-2017 --end=00:00:20 02-16-2017
We should see all the logs between 12pm and 8pm.