How to Use cURL With Proxy

How to Use cURL With Proxy

cURL with proxy is the easiest method for transferring data since it does not need a UI to be a support system for several protocols.

To begin, you use a proxy server that serves as a transfer hub between the user and the target location. You can view the proxy server as a middleman that receives incoming requests from users and sends these requests to the target location. The user thus accesses the internet via it as a gateway.

The cURL on the other hand is viewed as a communicator. It allows you to communicate with a server by defining the destination (which is most of the time in the form of a URL) and the information you wish to transmit. Almost all devices that send data over various internet protocols have cURL integrated into them.

This blog will walk you through using proxy with cURL to keep things simple. You can see this as a step-by-step guide on using cURL with proxy. Hence before you begin to cURL, I advise that you have a solid grasp of what proxies are and how to use them in browsers. This fundamental understanding will be quite helpful throughout this entire blog.

Are you new to this? First, become familiar with using proxies in this article on residential proxy vs data center proxy.

 

What Is cURL and Why Use It?

What is cURL

This article will focus on cURL and the wide range of functions it performs to benefit you as a developer, programmer, or simply a user of its features.

The command line utility cURL, also pronounced curl, means Client URL. cURL is a command line tool used to transport data to and from servers without requiring user input. You can use cURL to limit bandwidth, support proxies, authenticate users, support proxies, authenticate users, and many other things. This data is sent and received from different servers using the URL syntax:

cURL [options] [URL]

Client-side URL transmission software called libcURL command is used by the cURL command and supports close to 25+ protocols and formats. With one of the supported protocols including HTTP, HTTPS, SCP, SFTP, and FTP, you can download data using the cURL command.

cURL makes use of a transmission software called LibcURL. Below is a brief description of libcURL’s features:

LibcURL

The library for multiprotocol file transfers when using cURL with proxy is called libcurl. A few of the client-side URL transfer protocols that are supported by the libcURL library are TELNET, TFTP, LDAP, and more

In addition to user+password authentication (Basic, Digest, NTLM, Negotiate, Kerberos), file transfer resume, HTTP proxy tunneling, and SSL certificates.

libcURL is portable. It builds and operates in the same way on a wide range of operating systems including Windows and macOS.
libcURL also supports HTTP POST, HTTP PUT, FTP uploading, HTTP form-based upload, proxies, HTTP/2, and HTTP/3.

On this planet, libcURL is perhaps the most versatile, robust, and frequently used network transfer library.

cURLs Protocols and Formats

Fierst, let’s take a detailed look at protocols.

Protocols

The protocol is the language used to request data to be transferred, either in one way or the other. The protocol outlines precisely how to inform the server that data is on the way or to ask for data from it.

Protocols are often specified by the IETF (Internet Engineering Task Force), which is home to RFC papers that detail every aspect of how each protocol operates, including how clients and servers should behave, what data to deliver, and so on.

What Protocols Does cURL Support?

cURL supports protocols that provide “data transfers” in either or both directions. Since cURLmainly uses URLs (actually, URIs) as the input key that describes the transfer, we often limit ourselves to protocols that have a “URI format” specified in an RFC or are at least somewhat common.

As of this writing, the most recent version of cURL supports the following protocols:

  • DICT
  • FILE
  • FTP
  • FTPS
  • GOPHER
  • GOPHERS
  • HTTP
  • HTTPS
  • IMAP
  • IMAPS
  • LDAP
  • LDAPS
  • MQTT
  • POP3
  • POP3S
  • RTMP
  • RTSP
  • SCP
  • SFTP
  • SMB
  • SMBS
  • SMTP
  • SMTPS
  • TELNET
  • TFTP

 

The protocols often come in many versions or flavors, which further complicates problems.

The HTTP protocol is what cURL by default utilizes. cURL may also utilize the following protocols and file types:

  • File Transfer Protocol (FTP)

Files are sent via file transfer protocol from a server to a user. To upload these types of files, combine cURL with this protocol

cURL-target “selected file” “ftp:/[target-destination]”

An effective substitute for a typical FTP client is cURL. In a prior article, we gave a detailed description of SOCKS vs HTTP, you can check it out for more explanation.

  • Simple Mail Transfer Protocol (SMTP)

For transferring data to an SMTP server using the Simple Mail Transfer Protocol. Your text, the sender, and the recipient are all included in this data. Here’s how it appears:

cURL smtp://[smtp-server]– mail to [sender]– mail rcpt [recipient]-upload-file [mail-content-file]

  • The Dictionary Network Protocol [DICT]

Access to dictionaries is made possible through the Dictionary Network Protocol. You execute the following command using cURL while using it.
[ dict:/dict.org/d:hi” ] in a URL.
You get a response from this command that includes the Dictionary you specified and the definition of ‘hi’ inside.

 

Why Use cURL

cURL is commonly utilized by developers because it is versatile and effective. It can be used for a variety of functions including:

  • Authentication of Users
  • HTTP postings
  • File transfer
  • Resume
  • Metalink support
  • Proxy supports for FTP uploads and SSL connections
  • Provides a lot of information on what has been delivered and is helpful for troubleshooting.
  • It may have a rate limit.
  • Possibility to give URL fragments through enclosing fragments in parentheses e.g https://google.one,two, three.com
  • cURL can provide as many URLs as desired using the command line

cURLs’ most fundamental use case is downloading and uploading whole web pages using any of the supported protocols or formats.

 

The Differences Between Curl and Wget

cURL VS Wget

For a better understanding of how to use cURL with proxy, we have to know the similarities and differences between the cURL proxy command and the Wget command.

 

What Is the Wget Command?

Wget is a free Network file downloaded and command-line tool that has several features that make downloading files simple, such as:

  • Obtain huge files or mirror whole FTP or web pages
  • Obtain many files at once
  • Limits the download’s bandwidth and speed
  • Obtain files via proxies
  • Able to continue interrupted download
  • Mirror directories recursively
  • Is compatible with Windows and the majority of UNI X-like operating systems.
  • Running in the background or unattended
  • Persistence for HTTP connections is supported
  • Downloads for both IPv4 and IPv6

 

The syntax for Wget is as follows:
Wget [option] [URL] for $

cURL vs Wget: What Do Both Commands Do?

  • Both programs issue HTTP post requests and are command line utilities that can download files from FTP and HTTP or HTTPS.
  • Both are open-source software.
  • Support HTTP cookies, HSTS, and HTTP proxy, and are intended to operate without user intervention.
  • Both cURL and Wget initiatives got off in the year 1996 (under different names)
  • Both may operate on several operating systems and are portable.

 

How Do cURL and Wget Vary?

For a better knowledge of how both cURL and Wget operate, let us look at how they both function differently. Understanding their functions individually helps to know what makes them unique and distinct.

 

cURL

  • cURL is supported by a library known as libcURL. This library has a usable API for platforms. The distinction is quite significant because it results in the creation of how to run things internally. A library takes a little longer to create than a simple command line utility.
  • Everything in a cURL is in a pipe fashion. Since cURL operates more similarly to the standard Unix Cat command. Wget on the other hand uses a more similar analog to cp.
  • cURL is primarily designed to transmit data in a single operation. It does not have any kind of HTML parser or recursive downloading mechanism. URLs transmitted depend on what the user provides.
  • cURL supports different protocols. Examples include RTMP, RTSP, LDAP, POP3, IMAP, SMB, SFTP, TFTP, TELNET, DICT and SCP, SFTP, and TFTP. Wget supports HTTP(S) and FTP.
  • cURL is more portable than Wget.  It can be built and used on many more systems.
  • cURL supports additional HTTP authentication techniques, particularly when using HTTP proxies.
  • cURL supports HTTPS proxy. For using cURL with proxy, it supports SOCKS 4 and SOCKS 5 using name resolution depending on local or proxy. Wget does not support HTTPS proxy. If you need to know more you can check our prior article on SOCKS vs HTTP.
  • cURL can upload and transfer data in both directions. Wget only supports simple HTTP post requests.
  • cURL does automated decompression. It supports the content encoding formats: gzip, brotli, zstd, and deflates them. Wget on the other hand does support the decompression of transfer encoded HTTP.
  • cURL proxy command supports alt-svc. It also supports HTTP/2 and HTTP/3.
  • cURL performs dual-stack connections. When performing dual-stack (IPv4+IPv6) connections, cURL uses Happy Eyeballs.
  • cURL supports several parallel transfers (-z). cURL does more in parallel transfers than Wget.
  • cURL is preinstalled on Windows 10 and macOS. Wget is not.

 

Wget

  • Wget can only be used from the command line. The library (in the form of libcURL in cURL) is absent.
  • Wget supports recursive downloads. Wget’s ability to download recursively or download simply anything either an HTML page to an FTP directory listing from a remote resource- is one of its main advantages.
  • Wget and cURL both have GPLv3 licenses. The two command lines have similar licenses.
  • Wget does not need -o or -O to download a distant URL. cURL needs -o or -O to download a distant URL to a local file.
  • Wget supports SSL/TLS. For SSL/TLS, Wget supports only GnuTLS or OpenSSL.
  • Wget supports HTTP proxy. While using an HTTP proxy, Wget supports only basic auth.
  • Wget does not support SOCKS. cURL socks proxy exists as cURL supports SOCKS
  • Wget is dependent on gnulib. It demands a C99 compiler.

 

When to Use either cURL or Wget

  • Use the one that helps you finish the work first and foremost
  • Wget handles download retries over shaky connections maybe a little better than cURL and offers downloading capabilities that cURL lacks.
  • cURL is likely the better tool for the majority of other tasks.

 

3 Ways of Using cURL With Proxy

Let’s go over how you can send data over a proxy server using the cURL command line tool, in between a user and a destination server with a proxy server as a middleman.

Below is a detailed explanation of how you can use cURL with proxy in 3 different ways:

1. Using Command Line Parameters

Utilizing a command line parameter is the first and most straightforward method of using cURL with proxy. The command line has different options. We will be discussing the short option and long options.

Command-line options
When instructing curl to do a task, you run it with zero, one, or several command-line arguments together with the URL or collection of URLs you want the transfer to be about. More than 200 distinct options are supported by the curl

  • Short option

cURL receives instructions about how you want it to behave via command line arguments. For instance, you may use the -v option to tell curl to use verbose mode:
cURL —version http://example.com

Here, the “short option” -v is used. Those are written with a single letter directly after the negative sign, as shown.

  • Long option

Since there are just a few letters in the alphabet and there are many variables to be controlled, not all choices are accessible as single-letter alternatives, however, they are quick to compose and utilize. There are consequently long option names offered for such.

Additionally, the majority of short choices have longer name aliases as a convenience and to make scripts easier to understand.

Long options are usually typed with two dashes before the name, and only one option name may be written per double-minus.

cURL —verbose http://example.com is the long format request for verbose mode.
cURL—redirect http://example.com is the long format request for HTTP redirect

 

2. Using Environment Variables

Using cURL with proxy involves Curl checks to determine whether a proxy is asked to be used, for the presence of specifically defined environment variables.
A variable called [scheme] proxy, which stores the proxy host name, is set to indicate the proxy (the same way you would specify the host with -x).

The ‘HTTP proxy’ environment option must be set if you wish to instruct curl to utilize a proxy when it accesses an HTTP server. Much like this:

curl -v www.example.com
HTTP proxy=http://proxy.example.com:80

Even while the aforementioned example uses HTTP, you may of course also specify Ftp proxy, HTTPS proxy, and other types of proxies. Except for the HTTP proxy, all of the names of these proxy environment variables may also be given in capital letters, such as HTTPS PROXY.

All protocols may be controlled by a single variable, called ALL PROXY.

The NO PROXY on the other hand  variable is used this way:
Put a list of host names separated by commas that shouldn’t be accessible using a proxy in that field. To match all hosts, you may specify NO PROXY as a single asterisk (‘*’).

There is also a command line option called —no proxy that does the same task and functions similarly to the NO PROXY setting.

3. Using the [ .curlrc ] file

Setting up a config file might be useful for those who wish to use cURL with a proxy professionally and extract large volumes of data. Those who previously couldn’t specify an environment while using cURL command-line parameters on Windows may now do so using this method.

Simply said, this enables you to save the desired settings in a text file inside your system directory and then use it to modify your environment.
The benefits are clear.

You may save time and stop worrying about configuring an environment every time by generating several commands inside the config file.

 

cURL for Light Scraping

cURL for Light Scraping

Web scraping is a method of obtaining information from websites using a scraping bot, so the whole process is automated. The method enables quick, large-scale access to online data for users.

Curl may assist you in avoiding boring activities by automating the repetitious web scraping process. You must use PHP for it.

You can also quickly get a web page’s whole content using only one line of cURL code. Small-scale web scraping won’t cause issues, but as you make more queries, anti-bot systems may become active.

A helpful hint is to always follow the website’s regulations and avoid attempting to access password-protected material, which is often illegal or at the very least frowned upon.

 

Conclusion

Overall, using cURL with proxy is a versatile method that allows you to accomplish virtually any task, including making requests and configuring proxies.

As vast as Wget can be, cURL performs more in-depth HTTPS authentication than any other command line tool. With what we discussed so far, I bet you are considering giving cURL a shot. If you aren’t already, you should. Keep it cURLy (pun intended).