Curl Exercises

Julia Evans | Link

Recently I’ve been interested in how people learn things. I was reading Kathy Sierra’s great book Badass: Making Users Awesome. It talks about the idea of deliberate practice.

The idea is that you find a small micro-skill that can be learned in maybe 3 sessions of 45 minutes, and focus on learning that micro-skill. So, as an exercise, I was trying to think of a computer skill that I thought could be learned in 3 45-minute sessions.

I thought that making HTTP requests with curl might be a skill like that, so here are some curl exercises as an experiment!

What’s curl?

curl is a command line tool for making HTTP requests. I like it because it’s an easy way to test that servers or APIs are doing what I think, but it’s a little confusing at first!

Basic API

• curl $address - perform GET request to $address
• -i - show response headers
• -I - only show response headers
• -X POST - send POST request. Can be replaced with PUT or DELETE
• -H - set headers to send with request e.g. curl $address -H "Accept-Encoding: gzip
• -v, -vv - verbose mode
• -k - insecure, don’t verify security settings/certificates
• --cert, --key - use a client certificate
• --data, -d - send a POST request with data e.g. curl $address -d '{ "name" : "king' }' or curl $address @file.json. The send option will send a file which is handy if the data is quite large.
• copy as curl - in some developers tools this option is presented allowing one to download from the command line.

21 curl exercises

These exercises are about understanding how to make different kinds of HTTP requests with curl. They’re a little repetitive on purpose. They exercise basically everything I do with curl.

To keep it simple, we’re going to make a lot of our requests to the same website: https://httpbin.org. httpbin is a service that accepts HTTP requests and then tells you what request you made.

1. Request https://httpbin.org
2. Request https://httpbin.org/anything. httpbin.org/anything will look at the request you made, parse it, and echo back to you what you requested. curl’s default is to make a GET request.
3. Make a POST request to https://httpbin.org/anything
4. Make a GET request to https://httpbin.org/anything, but this time add some query parameters (set value=panda).
5. Request google’s robots.txt file (<www.google.com/robots.txt>)
6. Make a GET request to https://httpbin.org/anything and set the header User-Agent: elephant.
7. Make a DELETE request to https://httpbin.org/anything
8. Request https://httpbin.org/anything and also get the response headers
9. Make a POST request to https://httpbin.com/anything with the JSON body {"value": "panda"}
10. Make the same POST request as the previous exercise, but set the Content-Type header to application/json (because POST requests need to have a content type that matches their body). Look at the json field in the response to see the difference from the previous one.
11. Make a GET request to https://httpbin.org/anything and set the header Accept-Encoding: gzip (what happens? why?)
12. Put a bunch of a JSON in a file and then make a POST request to https://httpbin.org/anything with the JSON in that file as the body
13. Make a request to https://httpbin.org/image and set the header Accept: image/png. Save the output to a PNG file and open the file in an image viewer. Try the same thing with with different Accept: headers.
14. Make a PUT request to https://httpbin.org/anything
15. Request https://httpbin.org/image/jpeg, save it to a file, and open that file in your image editor.
16. Request https://www.twitter.com. You’ll get an empty response. Get curl to show you the response headers too, and try to figure out why the response was empty.
17. Make any request to https://httpbin.org/anything and just set some nonsense headers (like panda: elephant)
18. Request https://httpbin.org/status/404 and https://httpbin.org/status/200. Request them again and get curl to show the response headers.
19. Request https://httpbin.org/anything and set a username and password (with -u username:password)
20. Download the Twitter homepage (https://twitter.com) in Spanish by setting the Accept-Language: es-ES header.
21. Make a request to the Stripe API with curl. (see https://stripe.com/docs/development for how, they give you a test API key). Try making exactly the same request to https://httpbin.org/anything.