Exploring curl - Linux Commands
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!