Understanding cURL: A Guide

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Businesses need data that can be gotten from quality web scraping efforts. With cURL, web development and data retrieval (web scraping) proceed better. If you’ve ever researched web development, you must have heard about cURL. It’s a tool that has gained immense popularity amongst developers.

At first glance, it feels abstract, making you wonder what it’s used for. Hence, the need for this article where we duly examine what cURL is, what it’s used for, the issues that come with it, and how it can make your web scraping processes easier.

What is cURL?

The cURL (Client URL) library is a command-line tool designed to facilitate making requests, amongst other interactions with servers, using varying protocols. cURL made its way to the mainstream in 1997, becoming a significant part of the developer community.

Common uses of cURL

cURL has since found numerous benefits in the developer ecosystem. Here are some of the core uses to know about:

Sending HTTP requests

This is the primary function of the cURL library; sending HTTP requests to servers. There’s no limit to the type of request that can be sent via cURL. From simple GET requests to complex POST requests, cURL makes it all simple. The cURL library has simplified the complexities of these processes, making it easy for users to execute operations by inputting simple commands in the terminal. Furthermore, cURL can interact with APIs and fetch web pages, amongst other functionalities.

File transfer

cURL also makes it possible for files to be sent across the varying protocols on the internet. The cross-compatibility of the tool makes this possible. For instance, users can quickly get information from an FTP server while uploading to SFTP. The straightforward processes involved in carrying out activities with cURL are why it’s so popular amongst developers.

Testing APIs

Application Programming Interfaces are one of the core backbones of the Internet. With cURL, it becomes easier for developers to interact with APIs. This functionality rides on the essential ability of cURL to send requests on the internet. Beyond sending requests, cURL can also examine responses and debug issues, etc., during the development process.

Network troubleshooting

If you’ve used the internet as a technical person long enough, you must have experienced network issues at some points. You usually don’t know what’s wrong with your network and wait until it reloads, reboots, or miraculously clears up. cURL can help perform diagnostic checks, verify server responses, and cross-check the content of headers and other web pages. Doing all these on your behalf can determine and relate to your issue.

General issues of cURL

cURL is a powerful tool. But it also has its problems. Here are some common potential issues you’ll face while using a cURL proxy or other packages:

Authentication

The internet is filled with protected resources. Owing to this, you may run into some roadblocks when trying to access restricted content. Many contents online require authentication. Incorporating authentication within cURL requests can be tricky, especially with complex authentication processes like OAuth. Other token-based authentication procedures can also give you issues. The problem is, however, solvable, as you’d only need some additional configurations and parameters to get your cURL up and running again.

SSL/TLS certificate validation

By default, cURL performs SSL/TLS certificate validation, which it uses to secure network connections. Some issues are, however, expected in this case, especially when working with self-signed or improperly configured certificates. A fix could be modifying cURL options to turn off certificate verification.

Session management

cURL functions like a stateless infrastructure, meaning it doesn’t keep session information as the user executes requests. This is cool for some cases, but in situations like using a cURL proxy, performance may drop compared to other proxies.

More issues are bound to ensue when working with websites needing session-based authentication or cookies. Statelessness will result in skewed functioning. You’ll need to install some other scripts to use cURL when handling sessions and cookies.

How cURL is used for web scraping

Web scraping is one of the major use cases of cURL. Here’s how cURL is used for web scraping purposes.

Making HTTP requests

Web scrapers are tools designed to make requests on behalf of users. cURL comes into the process to make the request process easier. With a cURL command, destination URLs can be specified with additional parameters to get the desired website data. The cURL can also detail the storage process the extracted data should follow.

Handling cookies and sessions

When web scraping, some manual processes should be done. Examples of these are session management and handling cookies. cURLs can help with this with the ‘–cookie’ command prompt, which works to send and receive cookies when a browser makes a request. Efficiently handling cookies and sessions makes the scraping process more efficient.

Parsing HTML content

The data returned by web scrapers are a bunch of HTML content and folders. Combined with other tools like BeautifulSoup or JQ, cURL aids in parsing and extracting relevant data.

Automation

Automating scraping tasks is another use case of cURL. Rather than manually executing repetitive tasks, cURL can be combined with scripting languages like PHP, Python, or Bash. The tools developed by this combination can be used to implement multiple requests, navigate through paginated content, etc.

Conclusion

cURL isn’t the easiest tool for non-technical persons, but its use cases are vast once you get a hang of it. Though it may also come with some issues, the returns you get from it make the tool worth using.

I am a young digital marketer and a blog analyst, Author from Uttarakhand, India. I have been into blogging since 2013 and helping businesses with their SEO requirements. I have 12 years of experience; during the journey, I have worked on many websites and made good friends. I research and share my knowledge with everyone to help them succeed as solopreneurs, businessmen, and entrepreneurs. You can also find me on LinkedIn and see my entire journey.