What is a Curl command and how to use it? – Wingdings Translator Online

What is a curl command? It is a command available on most . It is an abbreviation for “Client URL”. Curl commands are designed to work as a way to check connectivity to URLs and as a great tool for transferring data. So let’s learn how you can start using it.

The Curl command supports the following list of protocols:

HTTP and HTTPS
FTP and FTPS
IMAP and IMAPS
POP3 and POP3S
SMB and SMBS
SFTP
scp
TELNET
GOPHER
LDAP and LDAPS
SMTP and SMTP

These are the most important supported protocols, but there are a few others as well. Curl works with libcurl, which is a free client-side URL parsing library.

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Check the version of Curl

As with any , before we start working with Curl, we need to log into our VPS. If you need help, check out this tutorial on .

First, let’s check which version of Curl is available with the following command:

curl –version

The output will show the Curl version with a list of supported protocols. Now we can see some examples of Curl commands.

Basic Curl Command Syntax

Let’s learn how to use Curl commands. The basic Curl syntax looks like this:

curl

The simplest use of Curl is to display the content of a page. The following example will display the home page of testdomain.com.

curl testdomain.com

This will generate the full source code for the domain’s home page. If no protocol is specified, curl will interpret it as HTTP.

Curl Script Options

Curl commands can download files from a remote location. You can do it in two different ways:

-EITHER will save the file in the current working directory with the same filename as the remote.
-either allows you to specify a different file name or location.

Curl Commands for Http

Curl can also be used when there is a proxy server. If you are behind a proxy server listening on port 8090 at sampleproxy.com, download the files as shown below:

curl -x sampleproxy.com:8090 -U username:password -O http:// testdomain.com/testfile.tar.gz

In the example above, you can omit -U username:password if the proxy does not require an authentication method.

A typical HTTP request will always contain a header. The HTTP header sends additional information about the remote web server along with the actual request. While you can check the header information through a browser’s developer tools, you can check it using a curl command.

Below is an example of how to retrieve header information from a website.

curl -I www.testdomain.com

Using curl, you can make a request GET and one POST. An application GET it will be like this:

curl http://mydomain.com

A sample of an application POST it will be like this:

curl –data “text=Hello” https://myDomain.com/firstPage.jsp

Here text=hello is the POST request parameter. This behavior would be similar to HTML forms.

You can also specify multiple HTTP methods in a single curl command. Do it using the option –nextSo:

curl –data “text=Hello” https://myDomain.com/firstPage.jsp –next https://myDomain.com/displayResult.jsp

This contains a POST request followed by a GET request.

Every HTTP request will have a user agent that is sent as part of the request. This indicates the details of the client’s web browser. By default, a curl request contains curl and the version number as the user agent details. An output of this would look like this:

“GET / HTTP/1.1” 200 “_” ”curl/7/29/0”

You can change this default user agent information using the following command:

curl -I http://mydomain.com –user-agent “My new Browser”

Now the modified result will be:

“GET / HTTP/1.1” 200 “_” ”My new Browser”

Cookie Curl

Curl commands can be used to check which cookies are downloaded at any URL. So if you’re accessing https://www.samplewebsite.comyou can cast to a file, save the cookies, and access them using cat or a VM editor.

The following is a sample of such a command:

curl –cookie-jar Mycookies.txt https://www.samplewebsite.com /index.html -O

Similarly, if you have the cookies in a file, you can send it to the website. An example of such a command is shown below:

curl –cookie Mycookies.txt https://www. samplewebsite.com

Curl for FTP

The Curl command supports FTP! You can use it to download files from a remote server.

curl -u username:password -O ftp://sampleftpserver/testfile.tar.gz

In the above command, ftp://sampleftpserver it is an FTP server that accepts connections. The username and password can be omitted for anonymous FTP connections. Type the command and watch the progress bar progress.

You can also upload files with the following command:

curl -u username:password -T testfile.tar.gz ftp://sampleftpserver

Again, we can omit the username and password for anonymous FTP connections.

Limit Curl Output

While using Curl, you can’t tell how big the output will be. You can restrict the bandwidth to make sure it’s not throttled by curl.

The following command restricts the bandwidth to 100K:

curl –limit-rate 100K http://testdomain.com/samplefile.tar.gz -O

conclusion

Curl is a powerful and widely used command. It is useful when you depend on the command line. It has several options and supports multiple protocols. That’s a very good reason to learn this command!

Remember, if you want to learn some advanced commands, just refer to the manual which should be in every version of Unix:

man curl

We hope this tutorial has given you a good starting point for using Curl! How will you use this command? Let us know in the comments!

Gustavo is passionate about creating websites. He focuses on the application of SEO strategies at for Spain and Latin America, as well as the creation of high-level content. When he is not applying new WordPress tricks you can find him playing the guitar, traveling or taking an online course.