Recap: Writing Data

Lesson 37 of 47 in Coddy's Networking with the Terminal course.

Sending data comes down to three decisions.

Which method. -d makes it a POST automatically; -X sets anything else. POST submits, PUT stores at a location, DELETE removes.

What the body is. -d 'a=1&b=2' for form data, a JSON string for an API. Use --data-urlencode for anything a human typed.

How you label it. curl says form encoded unless you say otherwise, so JSON needs -H 'Content-Type: application/json'. Forgetting it is the most common mistake in this chapter.

curl -s -X PUT -H 'Content-Type: application/json' \
     -d '{"role":"admin"}' http://127.0.0.1:9127/users/3

And when in doubt, point it at a listener and read the request back.

Challenge

Put the whole chapter into one request.

Start the capture listener on port 9127
Send a PUT to http://127.0.0.1:9127/users/3 with the JSON body {"role":"admin"}, correctly labelled
Print the request line, then the Content-Type line, then the body

Expected output:

PUT /users/3 HTTP/1.1
Content-Type: application/json
{"role":"admin"}

Try it yourself

Terminal

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Networking with the Terminal

1How Networks Talk

What Is a Network Clients and Servers IP Addresses Your First Request

4Is It Reachable?

ICMP and ping Reading Ping Output When Ping Lies Refused or Timed Out Recap: Reachability

7Sending Data

POST with -d What -d Actually Sends Form Encoding Sending JSON PUT and DELETERecap: Writing Data

2Names and DNS

Why Names Exist The Hosts File Looking Up a Name Record Types Recap: Names

5HTTP by Hand

Anatomy of a Request Request Methods Status Codes Response Headers Writing a Response Recap: HTTP Basics

8HTTPS and TLS

Why HTTPS The Scheme Picks the Port Certificates and Trust When TLS Fails Recap: HTTPS

3Ports and Sockets

What Is a Port Well-Known Ports Localhost Listening vs Connecting Recap: Ports

6curl in Depth

Seeing the Headers Saving Responses Custom Headers Status and Timing curl Exit Codes Recap: curl Flags

9Auth and Debugging

API Keys and Bearer The User Agent Timeouts and Retries Reading a Failure Recap: Debugging

Practice on your own: Terminal playground