curl

Additional Notes

curl sends requests to URLs and prints or saves the response. It supports HTTP, HTTPS, FTP, and many other protocols, but it is most commonly used for web requests and API testing.

Unlike a browser, curl shows you the request/response behavior directly, which makes it useful for debugging, scripting, and learning HTTP.

Syntax

curl [options] URL

Parameters

• options: Flags that change how curl behaves.
• URL: The URL to fetch or send data to.

Common Options

• -o FILE: Save output to a file.
• -O: Save using the remote filename.
• -L: Follow redirects.
• -I, --head: Show response headers only.
• -i: Include response headers in output.
• -X METHOD: Set HTTP method.
• -H HEADER: Add a request header.
• -d DATA: Send request body data.
• -u USER:PASS: Use basic authentication.
• -k, --insecure: Ignore TLS certificate validation errors.
• -v: Verbose connection details.
• -s: Silent mode.

Examples

curl https://example.com

Fetch a page and print it.

curl -L https://example.com

Follow redirects.

curl -O https://example.com/file.zip

Download a file using the remote filename.

curl -o page.html https://example.com

Save output to a specific file.

curl -I https://example.com

Show HTTP response headers.

curl -H "Authorization: Bearer TOKEN" https://api.example.com/me

Send an authorization header.

curl -X POST -H "Content-Type: application/json" -d '{"name":"test"}' https://api.example.com/items

Send a JSON POST request.

Practical Notes

• Use -L when downloads produce a small redirect page instead of the expected file.
• Use -I to inspect headers before downloading.
• Avoid pasting real tokens into shell history on shared systems.
• Use -k only for testing; it disables certificate verification.
• For simple file downloads, wget may be more convenient. For APIs, curl is usually better.