Understanding the curl Command

Basic Usage of curl

The curl command is a versatile tool for transferring data to or from a server using various protocols, including HTTP, HTTPS, FTP, and more. It is commonly used for making API requests, downloading files, and testing web services.

Common Options for curl

curl has a rich set of options that can be used to customize its behavior:

• -V, --version - Show version information and exit.
• -h, --help - Display help information and exit.
• -d, --data - Send specified data in a POST request.
• -X - Specify a custom request method to use (e.g., GET, POST).
• -H
  - Pass custom header(s) to the server.
• -o - Write output to the specified file instead of stdout.
• -O - Save the file with its original name from the server.
• -L, --location - Follow redirects.
• -u - Specify user and password for server authentication.
• -i - Include HTTP response headers in the output.
• -s, --silent - Silent mode (no output). Use with -S to show errors.
• --limit-rate - Limit the download speed to rate.

Examples of curl Command

Fetch a Webpage

This command retrieves the content of the specified URL.

Download a File

This command downloads the file and saves it with its original name.

Send Data in a POST Request

This command sends data to the specified API using a POST request.

Follow Redirects

This command follows any redirects until it reaches the final URL.

Send Custom Headers

This command includes a custom header in the request for authentication.

Understanding curl Output

The output of the curl command can include:

• HTTP Status Code: Indicates the result of the request (e.g., 200 for success).
• Response Body: Contains the data returned by the server.
• Response Headers: Metadata about the response (if using the -i option).

Summary of Options