Getting Started with cURL

What Is a Server?

A server is something that answers requests made by users.

Whenever we want data like a webpage, user details, or search results we send a request to a server, and the server sends back a response.

We talk to servers because:

• We want data

• We want to submit data

• We want some action to be performed (like login or form submission)

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How Do Requests Normally Work?

In daily life, your browser talks to servers for you.

For example:

• You open a website

• Click a button

• Submit a form

Behind the scenes:

1. Your computer sends a request to the server

2. The server processes it

3. The server sends back a response

You never see this process because the browser handles everything.

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Why Do Developers Need cURL?

Backend developers and programmers often want to:

• Test APIs

• Debug backend code

• Check server responses

• Send requests without a browser or app

This is where cURL comes into the picture.

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What Is cURL?

cURL is a command-line tool used to send requests to server and receive responses from servers.

In simple words:

cURL allows us to talk directly to a server from the terminal.

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Why Programmers Use cURL?

Programmers use cURL because:

• It lets them communicate directly with servers and APIs

• No browser or UI is needed

• It’s fast, lightweight, and powerful

• Perfect for testing and debugging APIs

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Making Your First Request Using cURL

Step 1: Open the Terminal

• macOS / Linux → Terminal

• Windows → Command Prompt or PowerShell

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Step 2: Type the following command

curl https://www.google.com

Press Enter. This is your first cURL request.

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What Just Happened?

• Your computer sent a request to Google’s server

• The server sent back the webpage data

• cURL printed the response directly in the terminal

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Understanding Server Responses

Whenever a server responds, it sends two things:

1. Status Code

Tells us whether the request succeeded or failed.

Common status codes:

• 200 OK → Everything worked correctly

• 301 Moved → Page has moved (redirect)

• 404 Not Found → Page doesn’t exist

• 500 Internal Server Error → Server error

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2. Data

The actual content returned by the server.

The data format depends on the API or request:

• HTML

• JSON

• Plain text

• Files (images, PDFs, etc.)

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Using cURL to Talk to APIs

An API (Application Programming Interface) is a server that:

• Expects a request

• Returns data in response (usually JSON)

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Example: GitHub API

Run this command:

curl https://api.github.com/users/octocat

What Happens?

• You send a request to GitHub’s API

• The server returns user data in JSON format

Example response:

{
  "login": "octocat",
  "id": 583231,
  "public_repos": 8,
  "followers": 3930
}

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GET Requests Using cURL

When you run:

curl https://api.github.com/users/octocat

It is a GET request by default.

GET Request:

• Used to fetch data from a server

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POST Requests Using cURL

A POST request is used to send data to the server.

Example:

curl -X POST https://api.example.com/products

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PUT : Update Existing Data

PUT is used to update an existing resource completely.

Simple meaning:

Replace the old data with new data.

Example:

Imagine a user profile:

Old data:

{
  "name": "Ankit",
  "age": 21
}

PUT request:

curl -X PUT -d "name=Ankit Kumar&age=22" https://api.example.com/users/1

New data:

{
  "name": "Ankit Kumar",
  "age": 22
}

PUT replaces the entire resource.

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PATCH: Partially Update Data

PATCH is used to update only specific fields.

Simple meaning:

Change only what is needed.

Example:

You only want to update the age.

curl -X PATCH -d "age=23" https://api.example.com/users/1

Result:

{
  "name": "Ankit Kumar",
  "age": 23
}

PATCH does not touch other fields.

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DELETE: Remove Data

DELETE is used to remove data from the server.

Simple meaning:

Delete a resource completely.

Example:

curl -X DELETE https://api.example.com/users/1

Result:

• User with ID 1 is removed from the server

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Common Mistakes Beginners Make with cURL

Expecting formatted output: cURL shows raw data, not pretty UI

Forgetting https:// in the URL

Forgetting -X for POST, PUT, DELETE requests

Sending data without -d

Example mistake:

curl -X POST https://api.example.com/products

Correct way (with data):

curl -X POST -d "name=phone" https://api.example.com/products