Exploring curl - Linux Commands

July 15, 2025

What is the curl Command in Linux?

The curl command in Linux is a versatile tool used to transfer data to or from a server, using a variety of protocols such as HTTP, HTTPS, FTP, and more. Unlike wget, which is mainly focused on downloading files, curl is designed to work with data transfers in both directions and is often used for testing APIs, uploading data, or interacting with web services.

Key features include:

Supports multiple protocols (HTTP, HTTPS, FTP, SMTP, SCP, SFTP, and more)
Can send custom HTTP headers and data (useful for APIs)
Supports HTTP methods like GET, POST, PUT, DELETE
Handles authentication (Basic, Digest, OAuth, etc.)
Supports cookies and session management
Ability to upload files or data
Shows detailed request/response headers for debugging
Works well in scripts and automation pipelines

Basic Syntax

curl [OPTIONS] URL

Example

curl https://example.com

This will fetch the content of the webpage and output it to the terminal.

Options

Option	What It Does	Example
`-o FILE`	Save output to a file	`curl -o backup.zip [URL]`
`-O`	Save with original filename	`curl -O [URL]`
`-L`	Follow redirects	`curl -L [URL]`
`-d DATA`	Send POST data	`curl -d "a=1&b=2" -X POST [URL]`
`-H HEADER`	Add custom header	`curl -H "Content-Type: application/json"`
`-X METHOD`	Set request method	`curl -X POST [URL]`
`-u USER:PASS`	Use basic auth	`curl -u user:pass [URL]`
`-s`	Silent mode (no output except result)	`curl -s [URL]`
`-I`	Show only headers	`curl -I [URL]`

Common Use Cases

Download and save a file with a custom name

curl -o backup.zip https://example.com/file.zip

Download and save with the original remote file name

curl -O https://example.com/file.zip

Follow redirects (e.g., from shortened URLs)

curl -L http://bit.ly/some-short-url

Send POST form data to an API

curl -d "username=username&password=password" -X POST https://api.example.com/login

Send JSON data with a custom header

curl -H "Content-Type: application/json" -d '{"name":"Victoria"}' -X POST https://api.example.com/users

Use basic authentication

curl -u user:pass https://api.example.com/secure-data

Download a file silently (no progress output)

curl -s -O https://example.com/largefile.iso

Fetch only HTTP headers (e.g., for debugging)

curl -I https://example.com

Additional Help

To see all available options:

curl --help
# or
man curl

Recap

The curl command is a powerful, flexible tool for transferring data over a variety of protocols. Whether you need to download files, interact with APIs, upload data, or troubleshoot HTTP requests, curl provides the control and options to handle these tasks efficiently.

By mastering curl, you’ll improve your ability to automate web interactions and debug network services from the Linux command line.

Happy curling! 🌐🚀

Thank you

Big thanks for reading! You’re awesome, and I hope this post helped. Until next time!