How to send data in HTTP request using cURL

HTTP, or Hypertext Transfer Protocol, is the foundation of data communication on the web. In many scenarios, it's necessary to send data as part of an HTTP request. This could be in the form of URL parameters, form data, or even as part of the request body.

cURL is a versatile tool that enables you to initiate HTTP requests from the command line. It supports various methods of sending data, from simple GET requests with URL parameters to POST requests with data payloads.

One of the primary uses of cURL is testing web services, especially in development environments. Whether it's sending form data or JSON payloads, cURL can handle it all. This article will guide you through various methods to send data in an HTTP request using cURL.

1. Open the terminal.
2. To send data as URL parameters in a GET request, use:

   $ curl "https://www.example.com/api?param1=value1&param2=value2"

3. To send data as form data in a POST request, use:

   $ curl -d "param1=value1&param2=value2" https://www.example.com/api

   With the -d flag, cURL uses POST by default.

4. If you need to send JSON data, use the following structure:

   $ curl -X POST -H "Content-Type: application/json" -d '{"key1":"value1", "key2":"value2"}' https://www.example.com/api

   Ensure that the Content-Type header is set to application/json when sending JSON payloads.

5. To send data in a PUT request, use:

   $ curl -X PUT -d "param1=value1&param2=value2" https://www.example.com/api

6. For sending data as multipart/form-data (such as file uploads), use:

   $ curl -F "file=@path_to_file" https://www.example.com/upload

   The -F flag makes cURL emulate a filled-in form in which a user has pressed the submit button. This causes cURL to POST data using the Content-Type multipart/form-data.

7. To customize headers when sending data, use the -H flag followed by the header:

   $ curl -H "Authorization: Bearer YOUR_TOKEN" -d "param=value" https://www.example.com/api

8. If you're dealing with an endpoint with SSL issues and wish to bypass them (mostly in development environments), use the –insecure flag:

   $ curl --insecure -d "param=value" https://www.example.com/api

   Using –insecure or its shorthand -k bypasses SSL certificate checks. This is risky in production environments.

By following these steps, you can easily use cURL to send different types of data in your HTTP requests. As always, refer to the official cURL documentation or use the man curl command to explore additional features and options.