cURL exploration

What is cURL?

Client URL (cURL) is a protocol that allows one to execute quick HTML requests from their terminal.

cURL commands use libcURL client-side URL transfer library which supports many different transfer protocols such as [[HTTP]], [[SMTP]], and [[FTP]]. On top of that, it also enables you to include cookies, set [[proxies]], and add auth credentials when making requests.

cURL comes pre-installed on Windows and MacOS

What is cURL used for?

• Testing APIs
• Downloading data from sources Since the terminal has access to the file system, cURL is able to download images from urls easily. For example here is a command to download the google logo and save it asgoogle-logo.png

cURL https://www.google.com/images/branding/googlelogo/2x/googlelogo_light_color_272x92dp.png > google-logo.png

• Testing websites
• Following redirects from the terminal
• Saving URL content Like downloading images, you can also save the content of a URL (a webpage) to a file.

cURL -o google.html https://www.google.com 

This command downloads the source code of Google’s home page and saves it as google.html

How to use cURL

The syntax of a cURL command is cURL [options] [URL]

Requesting data with cURL

Example cURL get request:

cURL https://jsonplaceholder.typicode.com/todos/1

Note: cURL commands ran with no [options] params will default to a get request. If you wanted to make the same request as above but with explicit params it would look like this:

cURL -X GET https://jsonplaceholder.typicode.com/todos/1

The -X flag tells cURL that you will be invoking a request method (like GET, POST, DELETE, PUT).

This request, when run in the terminal would return the following object:

{  
  "userId": 1,
  "id": 1,
  "title": "delectus aut autem",
  "completed": false
}

cURL Protocols and Formats

By default, cURL uses HTTP protocol but it does support other methods of transferring/requesting data.

FTP

cURL can be configured so it can use FTP (File Transfer Protocol). Doing so allows one to transfer files from a client to a server with a single command like this:

cURL -T [selected-file] "ftp://[target-destination]"

I should absolutely read into this more and see what ways people use cURL and FTP together.

SMTP

Simple Mail Transfer Protocol and cURL allows you to send emails from the command line of your computer:

cURL smtp://[smtp-sever] --mail-from [sender] --mail-rcpt \ [receiver] --upload file [mail-content-file]" https://blog.hubspot.com/website/curl-command