The Power of cURL: From Basic Commands to Advanced Usage

The cURL command-line tool is one of the most useful and versatile programs available. Its comprehensive HTTP implementation means that if there’s a URL for it, cURL can handle it. From fetching web pages and downloading files to installing software and checking IP addresses, cURL offers a wide range of functionalities that are essential for developers and power users.

8. Fetch a Web Page

In its simplest form, cURL fetches a URL and displays its contents directly in your terminal:

        curl info.cern.ch
    

Depending on the content type of the URL, you’ll see different outputs. For a web page, you’ll view its HTML source:

To save a web page, you can redirect the output to a file:

        curl info.cern.ch > info.cern.ch.html
    

Notice how cURL sends timing information to stderr when the output is redirected:

URLs containing special characters like ? or # must be carefully handled. Surround URLs with single quotes to avoid issues:

        curl 'info.cern.ch'
    

7. Download a File

When downloading binary files such as images or documents, the default behavior of cURL can be problematic:

        curl -o neo-the-cat.jpg https://placecats.com/neo/300/200
    

This saves the file locally. You can also use the -# or –progress-bar option for a progress bar:

        curl --progress-bar -o neo-the-cat.jpg https://placecats.com/neo/300/200
    

6. Install Software

Sometimes, software installation instructions use cURL. For example, the popular command-line history utility, Atuin, can be installed with a single line:

        curl --proto '=https' --tlsv1.2 -LsSf https://setup.atuin.sh | sh
    

This command downloads and runs a shell script hosted online. The curl options ensure secure and reliable execution. Always be cautious when running scripts downloaded from the internet.

5. Check Your IP Address