Beginner's Guide to cURL

Let’s quickly go through with the topics that we are going to cover in this blog.

What is cURL (in very simple terms)?
Why programmers need cURL?
Making your first request using cURL
Understanding request and response
Using cURL to talk to APIs
Common mistakes beginners make with cURL

What is cURL and why progrmmers need cURL?

Before understanding the cRUL let’s understand what is a server?

Server are basically a dedicated computers that provide services on the behalf of client such as ordinary desktop computers or workstation. So, it’s a centralised machine connected with multiple devices or client over the internet or LAN(Local Area Network). They connect with server for specific service. For example those services can be to retrieve a website, to access data or email and so on. A server could be dedicated to handle one service at a time for example webserver(only for retrieveing the websites) , mailserver(to send and receive the mails) and more. But it’s also possible to have a single server having all services included in it.

So, to talk with the server we as a client use the cURL, cURL is a widely used open source software consists of command line tool (curl) and a development library (libcurl) for transferring the data with URL syntax. It is mostly used by developer or administrator to automate tasks, testing APIs, upload and download files over a wide range of network protocols.

Server is a 24×7 running machine so to make that robust we can’t just use any ordinary desktop computers because they have some limitations which can’t handle more than a limit connections. So, the server consists of a processor ie intel XEON different than that of a ordinary computer processor ie Intel i7,i5.

Xeon processor support a multi-processor environment to distibute the workload(more than one porcessor are present) whereas ordinary computer support a single processor environment.

Xeon processor support ECC RAM(Error correcting code) which helps to maintain the robustness of a server by checking the processed data of RAM module, if there is an error it will correct it to prevent memory errors.

Making your first request using cURL, request , response and APIs.

Before running these commands make sure your device has pre-installed the curl, check on internet how to install curl on your paricular operating system.

Below —help command will show you the list of commands that you can use with the curl.

curl --help

This command will output all the content of the mentioned website.

curl https://hashnode.com

Below command will let you store the html code coming from the website into your local device with the file name save.html

curl -o save.html https://hashnode.com

It will show all the html content that you just pulled from the https://hashnode.com website.

cat save.html

It will store the response output html into the index.html file and you can see the file content using cat command.

curl -O https://hashnode.com/index.html

Let’s check below commands how redirecting checks are tested.

curl https://blog.meetabhinav.com

This command will extract all the content from my website.

Now let's check my catch all function that i set on my NameServe provider to redirect
https://meetabhinav.com to https://blog.meetabhinav.com


curl -L https://meetabhinav.com

Now this command will give me the content of the website blog.meetabhinav.com because its
gets redirected over there.

Now let’s know more interesting things, we can also check the response headers that are sent by webserver back to clients, the commands provided below.

curl -I https://hashnode.com

We can also see the TLS handshaking or client server communications execution using below command

curl -v https://hashnode.com

By the way GET is the default function assigned to curl command and if you want to use POST you can use the -d or —data command for example curl https://dummy_data//path -d “x = something & y = something” and this will POST into the server.

Search online on internet free api dummy data and select the method and copy paste the path and run the curl command to check the functionality.

Common mistakes beginners make with cURL

Skipping Documentation & Proper Research
Failure to Check Return Codes
Disabling TLS Certificate Checks
Ignoring Thread Safety Rules

And many more, google or search by yourself to know more.

Conclusion

You might get uncomfortable using cURL but don’t worry you will get it somedays. Do online research and try to learn the command and also impliment on your device to see the working of commands to know better.