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How To Use A Curl In Postman

API Testing Blog

Understanding cURL Commands

cURL is a powerful command-line tool that allows you to transfer data using various protocols, including HTTP. It’s a versatile tool for interacting with APIs, sending requests, and retrieving responses.

Let’s explore how to use cURL to send different types of requests and understand how to interpret the results.

Sending a GET Request with cURL

The simplest cURL request is a GET request, which retrieves data from a specific URL. Here’s a basic example:

Terminal window
curl https://api.example.com/users

This command will send a GET request to the URL https://api.example.com/users. You’ll see the response in your terminal.

Handling HTTP Headers

Many APIs require you to include headers in your requests for authentication or to specify data formats. You can set headers using the -H flag:

Terminal window
curl -H "Authorization: Bearer YOUR_API_KEY" https://api.example.com/users

This command includes an Authorization header with your API key.

Sending a POST Request

To send data to a server, such as creating a new user, you use a POST request. Here’s how to send a JSON request body:

Terminal window
curl -X POST -H "Content-Type: application/json" \
  -d '{"name": "John Doe", "email": "john.doe@example.com"}' \
  https://api.example.com/users
  • -X POST: Specifies a POST request.
  • -H "Content-Type: application/json": Sets the Content-Type header to indicate JSON data.
  • -d '{"name": "John Doe", "email": "john.doe@example.com"}': Provides the JSON data to be sent.

Using cURL for API Testing, Part 1: Validating Status Codes

cURL is an excellent tool for quickly testing API endpoints and checking their functionality. You can use the -I flag to retrieve just the HTTP headers, including the status code:

Terminal window
curl -I https://api.example.com/users

This will show headers like HTTP/1.1 200 OK, indicating a successful response. You can also use the -s flag to suppress the output for more streamlined testing.

Using cURL for API Testing, Part 2: Verifying JSON Responses

To test your API responses, you can easily validate JSON data with cURL using the -s flag for silent output and jq (a command-line JSON processor).

Terminal window
curl -s https://api.example.com/users | jq '.name'

This command retrieves the “name” field from the JSON response. You can use various jq expressions to extract and validate specific data points within your responses.

Exploring Advanced cURL Options

cURL offers a wealth of advanced options for managing cookies, timeouts, and more. Here are a few:

  • -c cookie_file and -b cookie_file: Manage cookies for persistent sessions.
  • -m timeout: Set a maximum time for the request.
  • --verbose: Provides detailed logging of the request and response.

Integrating cURL and Postman

While cURL is incredibly powerful, Postman is a user-friendly platform ideal for API development and testing. Postman provides a graphical interface for crafting requests, managing environments, and running tests.

You can use Postman to easily send cURL commands as requests and analyze responses. It’s a very convenient way to combine the power of cURL with a visually appealing workspace for API testing.

Remember Postman will convert your cURL command into a user-friendly interface with options for body, headers, authentication, and even pre-request scripts.

Wrapping Up

cURL is a valuable tool for developers and testers to interact with APIs directly and perform various actions. It’s especially helpful for quick checks, validation, and understanding how an API works. While cURL is a great command-line tool, Postman provides a more user-friendly interface and a comprehensive environment for managing and testing APIs.

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