Using cURL with proxy is one of the best methods for transferring data via networks, especially the internet. It requires little support setup and runs almost automatically.
We know that the proxy acts as a middleman between the user/client and server. It creates a gateway to filter information and enhance the security and privacy of data being exchanged on the network. The Client URL, or cURL, on the other hand, is a communicator, that is it exchanges information. It allows the client or user to communicate with a server by defining the destination (often in the form of a URL) and the information you wish to transmit to that destination.
Almost all devices that send data over various internet protocols have cURL integrated into them. Using it with proxies often leads to some interesting and extra capabilities.
This article will walk you through how to use a proxy with cURL. It is a detailed and step-by-step guide on everything you need to know about cURLs. But before you begin to explore cURL, you should try to have a solid grasp of what proxies are and how to use them. This fundamental understanding will be quite helpful.
If you’re new to proxies and how they work, consider reading this article on residential proxy vs data center proxy.
Now, let’s get started!
What Is cURL and Why Use It?
cURL (pronounced curl) is a command line tool that facilitates data transfer to and from servers. With a few lines of commands on a terminal, you can complete the exchange of huge chunks of data from any server to another.
Like every program command, cURL must follow a strict syntax for proper functioning. The syntax takes the form below.
cURL [options] [URL]
The ‘options’ part of the syntax denotes specific command parameters that indicate the desired result of the command. There are about 380 of these parameters or flags for cURL commands. A popular one is ‘-o’. It causes the content of a page to be delivered in a file.
cURL also requires a specific type of Uniform Resource Identifier(URI) to describe the transfer destination or origin, hence the URL part of the syntax. This specific URI format is the URL (Uniform Resource Locator). cURL doesn’t support network protocols that lack URLs. (Protocols are simply a set of instructions on how a server should request and/or receive data on a network.
In a prior article, we gave a detailed description of what protocols are and the difference between two popular ones: SOCKS vs HTTP. You should check it out for more explanation.)
cURL makes use of a transmission software called LibcURL. This is a library containing a list of multiple protocols that cURL supports. It is a robust and versatile and perhaps the most used network transfer library.
libcURL is a conventional and portable network software. It operates in the same way on a wide range of operating systems including Linux, Windows, and macOS. They are installed by default on these operating systems. However, if it is absent, you can download and install the software package from the cURL website.
What Protocols Does cURL Support?
cURL supports protocols that allow “data transfers” in either or both directions. Not all protocols support the use of URLs and such protocols are not compatible with cURL. Also, every protocol cURL supports has a predetermined format for how it can be deployed.
HTTP is the default protocol for cURL use. However, the command utility also works perfectly with lots of other network protocols including the following – arranged in alphabetical order:
- Dictionary Network Protocol [DICT]
- File Transfer Protocol (FTP)
Why Use cURL
cURL is commonly utilized because of its versatility, simplicity, and effectiveness. The fundamental purpose of cURLs is downloading and uploading whole web pages using any of the supported protocols or formats. It is also used for a variety of functions like user authentication, HTTP POST, file transfer, Metalink support, and proxy support for FTP uploads and SSL connections.
This robust use of cURLs is because of the following of characteristics of cURL:
- It provides detailed information on what has been delivered or sent and this is very helpful for troubleshooting.
- It supports multiple network protocols
- It can automatically try to work with another protocol when the specified protocol doesn’t work.
- It allows the possibility of specifying parts of a URL or multiple URLs to use by using URL fragments within a parenthesis
- It is compatible with different user environments (operating systems)
How to Use cURL
In order to use cURL, you must be sure it is installed on your device. If not, you have to download it from the cURL website.
A. Check if you have cURL installed on your device.
You can check if you have cURL installed on your system by doing this.
- On a Windows PC and a MacBook, open your command line interface or PowerShell terminal.
- Type ‘curl – -version’
- Press Enter.
If the software is installed on your device, you will get a message similar to this:
curl 7.55.1 (Windows) libcurl/7.55.1 WinSSL
Release-Date: 2017-11-14, security patched: 2020-11-05
Protocols: dict file ftp ftps http https imap imaps pop3 pop3s smtp smtps telnet tftp
Features: AsynchDNS IPv6 Largefile SSPI Kerberos SPNEGO NTLM SSL
curl 7.31.0 (x86_64-apple-darwin12.4.0) libcurl/7.31.0 OpenSSL/0.9.8x zlib/1.2.5
Protocols: dict file ftp ftps gopher http https imap imaps ldap ldaps pop3 pop3s rtsp smtp smtps telnet tftp
Features: IPv6 Largefile NTLM NTLM_WB SSL libz
If you see anything different, it means cURL is not present on your device and you have to install it.
B. Identify the right cURL syntax to use.
cURL utilizes the HTTP protocol by default. As such, its default syntax looks like this:
cURL [options] [URL]
Because cURL is compatible with multiple protocols, they are variations to how this syntax can be written. Each protocol has a slight modification of the syntax.
Here is what the cURL commands may look like with different network protocols.
- File Transfer Protocol (FTP)
cURL-target “selected file” “ftp:/[target-destination]”
- Simple Mail Transfer Protocol (SMTP)
cURL smtp://[smtp-server]– mail to [sender]– mail rcpt [recipient]-upload-file [mail-content-file]
- The Dictionary Network Protocol [DICT]
[ dict:/dict.org/d:hi” ]
It is important to know which network protocols you will be working on so you can get a perfect experience with cURL.
C. Use the right cURL syntax to achieve your aims
As mentioned earlier, there are a variety of things you can do with cURLs. You can use them to download and upload files, perform user authentication, and so on. Different cURL syntaxes are required for each of those tasks. The difference is mainly as a result of the kind of parameter that will achieve that aim and the network protocol you are using.
Some of the common tasks and the appropriate cURL command include:
- To download a file:
curl -o [file name] [URL]
- To upload a file using FTP protocol
curl -u [Username:Password] -O [ftp://URL]
- To request HTTP headers:
curl -I [URL]
How to Use cURL with Proxy
Using cURL with proxy allows for some interesting use cases. Tasks like web scraping require that you use a proxy alongside cURL to prevent site bans and blocks. In this section, you will learn how to send data over a proxy server using cURL.
The following steps describe how you can use cURL with a Proxy.
- Set Up The Proxy Server.
To use cURL with a proxy, you have to first set up your proxy. Your proxy provider will give you a set of instructions on how to do that. To confirm that your proxy is properly set up, input this in your terminal:
This command returns the IP address of your device. If the values match your device’s original IP address, your proxy server is not properly set up. Your proxy server is set up correctly if they don’t match.
2. Configure Your Proxy To Work With cURL Commands
There are three ways you can configure your proxy to work with cURL.
1) Using a configuration file [.curlrc]
A configuration file is simply a text file that comprises your desired settings. It will be saved in the .curlrc file format on your system directory so it is easily accessible when you run your cURL commands.
A configuration file for proxy settings will contain data in this format:
proxy = “[protocol://][host][:port]”
Multiple configuration settings can be saved in the file and activated whenever they are needed. Before you run your cURL commands, you will open the file. Afterward, any cURL command you deploy will always use the set proxy from the configuration file.
Creating a configuration file is the best method for those who use cURL with a proxy repeatedly and extract large volumes of data. It saves time by eliminating the need to configure the proxy for cURL every time.
2) Using command line arguments
This is great for one-time proxy use with cURL commands because you only have to use the direct cURL proxy syntax. This syntax is as follows.
curl -x “[protocol://][host][:port]” [URL] [options]
Remember the default protocol for cURL is HTTP. So, you must specify the protocol and details of the proxy server especially if you are using a different network protocol.
3) Using environment variables
The third method requires that you set the http_proxy and https_proxy variables. These variables are known as environment variables because they affect processes running at the system level. The commands are part of the operating system and are so powerful that they override every other parameter.
The syntax for cURL proxy settings via environment variables is as follows:
When you run these commands, any cURL command you run automatically executes via the proxy server.
cURL for Web Scraping
Web scraping describes the process of extracting large amounts of data from multiple websites. The process is usually automated with a scraping bot. However, websites have anti-bot mechanisms to block the process and protect their data.
Using cURL with proxies will assist in avoiding IP bans and make the process even faster and more efficient. You will get the whole content of a web page using only one line of cURL code. However, a rule of thumb is to check and follow the target website’s regulations and avoid attempting to access password-protected material, which is often illegal and frowned upon.
The Differences Between Curl and Wget
Wget is also a command-line tool that has several features that allows transferring files via standard network protocols like HTTP, HTTPS, And FTP. Its name is an amalgamation of the first letter of WWW and ‘get’. This is a nod to the fact that Wget was designed primarily for data exchange on the web.
The standard syntax for Wget commands is as follows:
Wget [option] [URL]
Wget commands are alternatives to cURL commands. They perform similar functions. However, they do it in different ways.
cURL vs Wget: The Similarities
- Both are command-line utilities that can download files from FTP and HTTP or HTTPS and support HTTP post requests.
- Both are open-source software
- Both cURL and Wget tools were introduced in the same year— 1996.
- Both have similar licenses – the GPLv3 license.
- Both are lightweight software packages and they operate on several operating systems.
How Do cURL and Wget Vary?
The major difference between cURL and Wget lies in the way both utilities execute the requests and the resources they use to achieve their aims. The following table highlights these differences better.
When to Use Either cURL or Wget
In many situations, cURL is often the best choice. However, there are instances where Wget is the obvious choice. You must identify which of these command line utilities will help you complete your tasks faster and more effectively. For example,
- Wget handles download retries over shaky connections better than cURL, and
- It offers downloading capabilities like decisive recursive downloads and bandwidth control that cURL lacks.
Therefore, the best choice would be to use Wget commands if you are in such situations.
Also, in situations where a network protocol other than HTTP/HTTPS, and FTP is used, cURL is the obvious choice. Wget commands are not compatible with those protocols. Your choice of when to use cURL or Wget will always depend on the peculiarities of the tasks you’re carrying out.
cURL commands are powerful and versatile tools for anyone working with transferring large volumes of data over a network. Using cURLs with proxies is the desired upgrade that allows you to accomplish virtually any task. This combination ensures data privacy and security without losing the versatility of the cURL commands. As vast as Wget can be, cURL is preferable because of its easy-to-use and powerful capabilities.
With what we discussed so far, I bet you are considering trying out the cool effects of cURL. If you aren’t, you should. Stay cURLy (pun intended).