A cURL is a command-line tool that is responsible for transferring data in the network. A command line is a process of instructing the Operating System through commands. In the same way, this cURL tool allows users to pass information to servers on the internet through simple commands.
sudo apt install curlOne important command among many cURL commands that everyone should know is the ‘help’ command. Here are the steps to use the help command.
curl -- helpcurl --help categorycurl --help proxyHere are some popular commands and their syntax.
| –help | Displays the commands |
| –help <category> | Gets help |
| –data <data> | HTTP post data |
| –fail | Fails silently on HTTP errors |
| –include | Includes the protocol responses in the header |
| –output <file> | Writes the output of a file |
| –user <user: password> | Server user and password |
Here, let’s discuss a few simple examples of cURL commands.
Every cURL command starts with the word ‘curl’ which is followed by the actual instruction to the system from the cURL command-line tool.
curl https://www.proxyscrape.com/homeThis displays the HTML code of the page.
curl https://www.proxyscrape -IThis command displays the header information of the website.
Users can configure the default proxy protocol with cURL requests. This lets users access information anonymously. Here is the cURL command-line to set up a proxy in a cURL request.
curl --proxy [protocol://]host[:port]curl --proxy http://159.65.133.175 https://www. httpbin.org/ip/In this example, we are configuring the proxy server of our localhost with the HTTPS request to access the desired URL.
In this case, we are using two URLs. The first one is the proxy address (http://159.65.133.175) that we are configuring with the HTTP request. The second one (httpbin.org/ip/) is the URL that we wish to access with the proxy address.
Now, this HTTP request is secured with the proxy settings.
If you want to explore other commands related to this proxy, use the help command with the proxy category.
curl –help –proxyUsers can also include authentication to HTTP proxy servers. The authentication cURL command begins with the –U flag and further proceeds with the username and password attributes to ensure security.
Here is the basic syntax of the authentication command:
curl -U --proxy-user <user:password>curl --U user: password --proxy http://159.65.133.175 https://www.httpbin.org/ip/If the password contains any special characters, make sure to enclose it with double quotes.
curl --U "user: P@ssword" --proxy http://159.65.133.175 https://www.httpbin.org/ip/If the user is not ready to pre-define the password, they can just include the “user” variable and leave it without adding the password as shown below. Running this command prompts the user to enter the password while executing commands.
curl --U user --proxy http://159.65.133.175 https://www.httpbin.org/ip/Explore other authentication commands using the “help” command.
curl –help authProxy users mostly prefer cURL proxies for debugging purposes because cURL proxies can effectively handle security errors with a –k flag. SSL certificate errors may reject HTTP requests if it finds them not secured. In this case, the HTTP proxy with cURL commands uses the –k flag to ignore the security errors.
curl --U user: password --proxy http://159.65.133.175 https://www.httpbin.org/ip/ -k [URL]People can use environmental variables with proxies. Users can define environment variables for each protocol they use. If they use HTTP protocols, they can define an HTTP proxy address to the variable names “http_proxy” or “https_proxy.” Whenever there is a need to use the HTTP proxy server, the users can make use of this global proxy without specifying the proxy URL each time.
export http_proxy="http://159.65.133.175"
export https_proxy="http://159.65.133.175"Using the alias command is another simple way of permanently configuring proxies. In this case, users can configure a proxy command to another proxy command.
alias curl= "curl -x http://159.65.133.175"Here, the word “curl” in the command is defined with another command line “–x http://159.65.133.175.”
curl https://www.httpbin.org/ip/In this sample, the word “curl” in the command refers to the HTTP cURL proxy. The actual meaning of the command-line is similar to the command shown below.
curl --proxy http://159.65.133.175 https://www.httpbin.org/ip/Here is another simple way of configuring a proxy server to avoid passing it each time. By creating a cURL configuration file (.curlrc file), users can create a home directory and include multiple proxy configurations.
proxy = "http://159.65.133.175"People may need to bypass proxies manually for certain cases, though they have set proxies globally through cURL features, like environment variables, aliases, or cURL files. In this case, you can use the –no proxy command to bypass the proxy address.
curl --no proxy "*" https://www.httpbin.org/ip/As we already know the cURL command supports most of the protocols, here we have an example with the socks protocol. Here we use a socks proxy instead of the HTTP proxy, which we have discussed so far.
curl --socks5 "159.65.133.175" https://www.httpbin.org/ip/People can include user authentication for the socks5 protocol.
curl --socks5 "159.65.133.175" https://www.httpbin.org/ip/Passing information to and from websites through the command-line tool is the basic ideology of cURL commands. If you wish to secure cURL commands with proxy features, like scraping ability, anonymity, and other debugging services, try a default proxy server to run on your device and configure it with cURL. Use help commands to learn more about cURL command-line arguments.