Master the Linux ‘curl’ Command: A Comprehensive Guide

This article provides a detailed introduction to the use and techniques of the Linux command-line tool curl. The content includes the history of curl, when and why to use it, how to use it, commonly used parameters with detailed examples, other supported parameters, most common use cases, advanced skills, and points to note. By reading this article, you will be able to master the basic usage and advanced techniques of the curl command, providing assistance for better use of the curl command in practical applications.

Instructions

This article provides a detailed guide for beginners to learn about the Linux ‘curl’ command, its history, usage, commonly used parameters, and some advanced techniques.

History

The ‘curl’ command was created by Daniel Stenberg in 1997. It is an open-source project and has become a widely used tool for transferring data between servers and clients using various protocols.

When and why to use it

‘curl’ is used to transfer data over a network using various protocols like HTTP, HTTPS, FTP, and more. It is helpful in fetching web pages, downloading files, and interacting with APIs. It is a powerful and flexible command-line tool that is widely used by developers, system administrators, and others who work with network communication.

How to use it

To use the ‘curl’ command, simply type ‘curl’ followed by the URL you want to fetch or interact with:

curl [<https://example.com>](<https://example.com/>)

The commonly used parameters

• -o Save the fetched file with the specified name
• curl -o output.html [<https://example.com>](<https://example.com/>)
• -O Save the fetched file with its original name
• curl -O [<https://example.com/file.txt>](<https://example.com/file.txt>)
• -I Show only the header information of a URL
• curl -I [<https://example.com>](<https://example.com/>)
• -X Specify a custom request method (GET, POST, PUT, DELETE, etc.)
• curl -X POST [<https://example.com/api>](<https://example.com/api>)
• -d Send data in a POST request
• curl -d "param1=value1&param2=value2" [<https://example.com/api>](<https://example.com/api>)

Other supported parameters

• -u Specify a username and password for authentication
• -H Add custom headers to the request
• -L Follow redirects
• -k Allow insecure connections
• -s Run in silent mode

Most common use cases

• Fetching web pages
• curl [<https://example.com>](<https://example.com/>)
• Downloading files
• curl -O [<https://example.com/file.txt>](<https://example.com/file.txt>)
• Interacting with REST APIs
• curl -X POST -d "data=value" [<https://example.com/api>](<https://example.com/api>)

The tricky skills

• Uploading a file using FTP
• curl -u username:password -T file.txt [<ftp://example.com/upload/>](<ftp://example.com/upload/>)
• Posting JSON data to an API
• curl -X POST -H "Content-Type: application/json" -d '{"key":"value"}' [<https://example.com/api>](<https://example.com/api>)

What needs to be noted

• Be cautious when handling sensitive data, as ‘curl’ command history may be stored in your shell history.
• To securely transfer data, always use HTTPS or other secure protocols.

Conclusion

The ‘curl’ command is a powerful and flexible tool for transferring data over various network protocols. Understanding its basic usage, parameters, and advanced techniques can help you efficiently interact with servers, APIs, and other network resources.