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What is cURL Command and How to Use It?

Yelyzaveta Nechytailo

2024-11-183 min read
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In today's fast-paced digital environment, managing data transfers and testing web-based applications has become essential. One tool that has stood the test of time for developers and system administrators alike is cURL. In this post, we’ll explore what is cURL, why it’s widely used, and how you can use it effectively in your projects.

What is cURL?

cURL (pronounced as “curl”) is an open-source command-line tool and library that enables data transfer using various network protocols, such as HTTP, HTTPS, FTP, IMAP, and more. It’s often used to interact with APIs, download files, or test server responses. The name "cURL" stands for Client URL, reflecting its purpose of working with URLs to retrieve or send data.

The tool supports a wide range of features, including:

  • Data retrieval and submission: cURL allows you to fetch data from a URL (e.g., downloading web pages or files) or submit data (e.g., sending form data or interacting with APIs).

  • SSL/TLS security: Supports secure data transfer using SSL/TLS, ensuring encrypted communication over HTTPS, which protects sensitive information from being intercepted. Check out our blog post to learn how to effectively ignore SSL certificate with cURL.

  • Proxy support: Can route requests through a proxy server, enabling users to anonymize their IP, bypass geo-restrictions, or test how their applications perform in different locations. See more information on how to use cURL with proxy

  • Data compression and decompression: Supports handling compressed data formats such as gzip or deflate, allowing faster data transfer and reducing bandwidth usage by sending or receiving compressed content.

  • Authentication for restricted resources: Provides options for various authentication methods (e.g., Basic, Bearer, OAuth), enabling secure access to protected resources like APIs, private servers, or login-restricted websites.

Why use cURL?

cURL offers several advantages that make it an indispensable tool:

  1. Versatility: It supports multiple protocols, making it a one-stop solution for various data transfer needs.

  2. Lightweight: No need for a graphical interface; it runs directly in the terminal.

  3. Easy to use: Allows to perform complex tasks, such as sending GET or POST requests, downloading files, or even automating data interactions.

  4. Debugging and testing: Developers often use cURL to test RESTful APIs, ensuring that their applications can communicate with external services.

  5. Cross-platform: Available on virtually every operating system, including Linux, macOS, and Windows. We have a blog post on using cURL for downloading files in Linux – check it out for more detailed insights.

  6. Script-friendly: Its command-line nature makes it easy to integrate into scripts for automation.

How to use cURL?

Let’s dive into some practical examples to understand how to use cURL effectively:

1. Basic GET request

Retrieve the contents of a web page:

curl https://sandbox.oxylabs.io/products/1

This command fetches the HTML content of the specified URL, displaying it directly in the terminal. It is commonly used to quickly view or test website content.

2. Download a file

Save a file from a remote URL:

curl -O https://sandbox.oxylabs.io/assets/action-adventure.svg

The -O option saves any type of file with its original name in the current directory, making it easy to download files without specifying custom names.

3. Send a POST request

Submit data to a server using the POST method:

curl -X POST -d "your data" https://httpbin.org/post

Here, -X POST specifies the request method, while -d sends data in the request body. This is often used to submit form data or interact with APIs requiring POST requests. If a successful POST request provides a redirect URL, you can simply use the -L flag to follow redirects and the -d flag to POST data:

curl -L -d "username=admin&password=12345" https://quotes.toscrape.com/login

4. Set custom headers

Add custom headers, often used when working with APIs:

curl -H "Authorization: Bearer your_token" https://httpbin.org/headers

The -H flag allows you to include custom headers, such as authorization tokens, which are essential for accessing secured endpoints or providing additional context to requests.

5. Download and save with a custom name

Use -o for downloading files with a specific name:

curl -o custom_name.html https://sandbox.oxylabs.io/products/1

Unlike -O, the -o option lets you define a custom filename for the downloaded file, giving more control over how files are saved.

6. Test REST APIs

Fetch JSON data from an API:

curl https://scraping-demo-api-json-server.vercel.app/products

This command retrieves data from the specified API endpoint, often returning JSON. You can enhance readability by piping the output to tools like jq for formatted JSON display. You can download jq for your device from the official website and then run the following curl command:

curl https://scraping-demo-api-json-server.vercel.app/products | jq

Here’s what the JSON output should look like:

7. Upload a File

Use the -F flag to upload files:

curl -F "field_name=@path/to/yourfile.txt" https://example.com/upload

The -F option is used for file uploads, allowing you to send a file as part of a multipart/form-data request, typically for forms that require file submissions. Note that field_name is the name of the form field where you want to upload the file.

Conclusion

cURL is a powerful, versatile tool for data transfer and testing web services. Whether you’re fetching data, submitting forms, or debugging APIs, cURL simplifies these tasks with minimal effort. With a few commands, you can automate and streamline your workflow, saving time and enhancing productivity.

Learn more about cURL by discovering cURL Converter – your go-to tool for transforming cURL commands into your preferred programming languages.

Frequently asked questions

What is the use of the cURL command?

The cURL command is used for transferring data across different protocols like HTTP, HTTPS, FTP, and more. It’s commonly utilized for interacting with APIs, downloading files, and testing server responses.

Why use the cURL command?

cURL is widely used because it’s versatile, script-friendly, cross-platform, and supports a variety of protocols, making it ideal for data transfers, API testing, and debugging.

What is the cURL option used for?

cURL options modify the behavior of the command. For instance, -X specifies the request method, -d sends data in the request body, and -O saves files with their original names.

What does the cURL command represent?

The cURL command represents a way to interact with servers over various protocols to send and receive data. It provides a simple interface for transferring data and testing web services.

What does cURL stand for?

cURL stands for Client URL, highlighting its ability to handle URL-based data transfers.

What is the cURL command in REST API?

In REST API development, the cURL command is used to test endpoints, send requests (GET, POST, PUT, DELETE), and debug responses by interacting with the API directly from the command line.

About the author

Yelyzaveta Nechytailo

Senior Content Manager

Yelyzaveta Nechytailo is a Senior Content Manager at Oxylabs. After working as a writer in fashion, e-commerce, and media, she decided to switch her career path and immerse in the fascinating world of tech. And believe it or not, she absolutely loves it! On weekends, you’ll probably find Yelyzaveta enjoying a cup of matcha at a cozy coffee shop, scrolling through social media, or binge-watching investigative TV series.

All information on Oxylabs Blog is provided on an "as is" basis and for informational purposes only. We make no representation and disclaim all liability with respect to your use of any information contained on Oxylabs Blog or any third-party websites that may be linked therein. Before engaging in scraping activities of any kind you should consult your legal advisors and carefully read the particular website's terms of service or receive a scraping license.

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