cURL, which stands for “Client URL,” is a command-line tool used for transferring data to or from a server. It supports a wide range of protocols, including:
- HTTP
- HTTPS
- FTP
- SMTP
- And many more
It is a versatile tool that works across various operating systems, including Linux, macOS, and Windows.
What is it used for?
cURL is primarily used for:
- Downloading files: You can use it to download files from web servers, FTP servers, and other sources.
- Making API requests: It is a popular tool for testing and interacting with APIs. It allows you to send various types of requests (GET, POST, PUT, DELETE, etc.) and include headers, data, and authentication credentials.
- Fetching web page content: It can retrieve the HTML content of a web page, which can be useful for debugging or scripting.
- Testing server connectivity: It can be used to check if a server is responding correctly.
- Automating tasks: It can be incorporated into scripts to automate data transfer tasks.
Why use cURL?
- Versatility: It supports a wide range of protocols and options, making it suitable for various tasks.
- Command-line interface: It’s command-line interface makes it efficient for scripting and automation.
- Wide availability: It is pre-installed on many operating systems and is easy to install on others.
- Open source: It is open-source software, which means it’s free to use and distribute.
Basic cURL syntax
The basic syntax of a command is:
curl [options] [URL]
- curl: The command itself.
- [options]: Optional flags that modify the behavior of the command.
- [URL]: The URL of the resource you want to access.
Common options
These are some commonly used cURL options:
- -O: Downloads the file from the URL and saves it with the same name as the remote file.
- -o: Downloads the file from the URL and saves it with a specified name.
- -X: Specifies the request method to use (e.g., GET, POST, PUT, DELETE).
- -H: Sends a custom HTTP header with the request.
- -d: Sends data with the request, typically used for POST requests.
- -u: Provides username and password for authentication.
Examples of commands
Here are a few examples of what a real cURL command would look like:
Get the content of a web page:
Bash
curl https://www.example.com
Download a file:
Bash
curl -O https://www.example.com/file.txt
Send a POST request with data:
Bash
curl -X POST -d “name=John&age=30” https://www.example.com/api/users
Send a JSON payload:
Bash
curl -X POST -H “Content-Type: application/json” -d ‘{“name”: “John”, “age”: 30}’ https://www.example.com/api/users
Conclusion
cURL’s is a very useful tool for developers, system administrators, and anyone else needing to interact with servers from the command line.