What is cURL?

cURL (short for Client URL) is a command-line tool you can use to transfer data to or from a server using various network protocols. It’s a versatile tool that allows you to make different types of requests, like downloading files, sending data, and interacting with APIs.
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Related terms: API | wget | Web scraping | Selenium | Python

What is cURL?

cURL is a command-line tool that allows you to communicate with servers using a wide range of protocols, including HTTP, HTTPS, FTP, SCP, and many more. Because it’s a command-line tool, it doesn’t have a graphical user interface (GUI) like a web browser does. Once you’ve downloaded the software package including its library libcurl, you can interact with it by typing commands in a terminal or console window.

At its core, cURL is written in the C programming language. This code handles the complexities of network communication, including establishing connections, sending and receiving data, and handling different protocols.

cURL is short for Client URL. This is because it’s a tool that allows a client (like your computer) to interact with a URL (usually a server or a web resource). It is essentially a way to send and receive data from the command line, making it a popular choice for developers, system administrators, and anyone who needs to interact with web services or APIs.

What is cURL used for?

cURL has a wide range of applications in web development, system administration, and data extraction.

Testing APIs

cURL is a popular choice for developers to test APIs (Application Programming Interfaces). It allows you to send various types of HTTP requests, such as GET, POST, PUT, and DELETE, to interact with an API endpoint. You can then examine the API's response to ensure it's functioning correctly and returning the expected data. This is crucial for developing and debugging web applications that rely on APIs.

Downloading files

cURL can download files from various sources, including web servers, FTP servers, and cloud storage services. You can use it to download individual files or even automate the download of multiple files using scripts. This makes it a handy tool for retrieving data, software updates, or any other type of file from the internet.

Uploading data

cURL isn't just for downloading; it can also upload data to servers. This can be useful for tasks like submitting web forms, uploading files to a server, or sending data to an API endpoint. cURL provides options to specify the data you want to upload and the method for uploading it.

Debugging network connections

When you encounter network problems, cURL can be a helpful diagnostic tool. You can use it to send requests to specific servers or websites and analyze the responses. This can help you identify network connectivity issues, pinpoint errors, and troubleshoot problems with web services or APIs.

Web scraping

While dedicated web scraping tools might be more suitable for complex tasks, you can use cURL for basic web scraping. You can use it to download web pages and then extract data from the downloaded HTML content using command-line tools or scripting languages. This can be useful for extracting small amounts of data or for tasks that don't require complex interactions with the website.

How to use cURL

cURL is a command-line tool, so you interact with it by typing commands in a terminal. The basic syntax is:

curl [options] [URL]

For example, to download a file from a website, you would use:

curl -O https://www.example.com/myfile.zip

You can customize your cURL request using options like:

  • -X [method]: Specify the HTTP method (GET, POST, PUT, DELETE).
  • -H [header]: Add custom headers to the request.
  • -d [data]: Send data with the request.
  • -o [filename]: Specify the output filename.

You can find a complete list of options by typing man curl in your terminal.

For a more detailed guide on using cURL, read this step-by-step guide for using cURL in Python with proxies.

cURL and web scraping

You can use cURL for web scraping, especially for simple tasks or when interacting with APIs. You can use it to download web pages and extract data using command-line tools or scripting languages. However, for more complex web scraping tasks that involve JavaScript rendering, form interactions, or handling dynamic content, dedicated web scraping tools like Selenium are often more suitable.

cURL vs. wget

cURL and wget are both popular command-line tools for transferring data, but they have different strengths:

  • cURL: More versatile for interacting with APIs and handling complex HTTP requests.
  • wget: More robust for downloading files and mirroring websites.

Choosing between cURL and wget depends on your specific needs and the complexity of the task.