Mastering Linux's Curl Command: A Comprehensive Guide

The curl command in Linux is a powerful tool used for transferring data to and from servers using various protocols, including HTTP, HTTPS, FTP, and more. It is widely utilized for interacting with web APIs and downloading files.

Basic Syntax

The basic syntax of the curl command is:

curl [options] [URL]

Common Options

Here are some commonly used options with curl:

-O or --output

Save the output to a file with the same name as the remote file.

nbash n curl -O

-o [filename]

Save the output to a specified file.

nbash n curl -o [filename]

-L or --location

Follow redirects.

nbash n curl -L

-I or --head

Fetch the HTTP headers only.

nbash n curl -I

-d [data] or --data [data]

Send data in a POST request.

nbash n curl -d [data]

-X [command]

Specify a custom request method, such as GET, POST, PUT, DELETE, etc.

nbash n curl -X [command]

-H [header]

Add custom headers to the request.

nbash n curl -H [header]

-u [user:password]

Provide user authentication.

nbash n curl -u [user:password]

Examples

Basic GET Request

This retrieves the content of the specified URL and displays it in the terminal.

nbash n curl

Download a File

This downloads from the specified URL and saves it in the current directory.

nbash n curl -O

Follow Redirects

This follows any redirects that the URL might have.

nbash n curl -L

Send a POST Request

This sends a POST request with the specified data.

nbash n curl -X POST -d [data]

Fetch HTTP Headers

This retrieves and displays the HTTP headers sent by the server.

nbash n curl -I

Use Cases

API Testing

Developers often use curl to test RESTful APIs by sending requests and analyzing responses.

File Transfers

It can be used to download files from the internet or upload files to a server.

Web Scraping

curl can fetch web pages for scraping purposes.

Conclusion

curl is a versatile command-line tool that can handle a wide range of data transfer tasks. Its flexibility with options allows users to customize requests according to their needs. For further details, you can always refer to the man page by typing man curl in the terminal.