What is cURL?

cURL (client URL) is a command-line tool for transferring data to and from a server. It supports HTTP, HTTPS, and many other protocols, and runs on almost every platform. This makes cURL ideal for testing API communication from any device with a command line and network connectivity.

The most basic command is curl [URL]. The curl command followed by a URL retrieves the resource at that address — for a web page, it returns the HTML source.

To use cURL with REST APIs, you specify different HTTP methods along with headers and data. Here are common examples:

1. GET Request — retrieve data from the server:

   curl http://api.example.com/resource

2. POST Request — send data to the server (JSON in this case):

   curl -X POST -H "Content-Type: application/json" -d '{"key":"value"}' http://api.example.com/resource

3. PUT Request — update existing data on the server:

   curl -X PUT -H "Content-Type: application/json" -d '{"key":"value"}' http://api.example.com/resource/id

4. DELETE Request — delete existing data from the server:

   curl -X DELETE http://api.example.com/resource/id

In these examples, -X specifies the HTTP method, -H sets request headers, and -d sends data in the request body.

The actual commands vary based on the API's specifications. Always refer to the API documentation for accurate request formats.

Key cURL Resources

• The Tutorial from the official cURL website

  • https://curl.se/docs/tutorial.html

• The open source cURL book from the Everything cURL website

  • https://everything.curl.dev/index.html