Cheatsheet & Examples: curl
Download a webpage
Example Usage:
curl example.com
What it does:
Fetches the content of the webpage at example.com and displays it in the terminal.
Command-line Arguments Explained:
example.com: The URL to fetch the content from.
Upload data via POST
Example Usage:
curl -X POST -d "data=example" http://example.com/api
What it does: Sends data to the specified URL using the HTTP POST method.
Command-line Arguments Explained:
-X POST: Specifies the HTTP request method as POST.-d "data=example": Sends the given data in the request body (used with POST/PUT).
Send custom headers
Example Usage:
curl -H "User-Agent: Mozilla" -H "Accept: application/json" example.com
What it does: Adds custom HTTP headers to the request (e.g., User-Agent, Accept).
Command-line Arguments Explained:
-H "Header: Value": Specifies a custom HTTP header to include in the request.
Follow redirects automatically
Example Usage:
curl -L http://short.url
What it does: Automatically follows HTTP redirects (e.g., 301, 302) to the final destination.
Command-line Arguments Explained:
-L: Tells curl to follow redirects.
Save output to a file
Example Usage:
curl -o output.html example.com
What it does:
Saves the fetched content to a file named output.html instead of printing it to the terminal.
Command-line Arguments Explained:
-o output.html: Specifies the filename to save the output to.
Retrieve HTTP headers only
Example Usage:
curl -I example.com
What it does: Fetches the HTTP headers of the specified URL without the body content.
Command-line Arguments Explained:
-I: Outputs only the HTTP headers.
Use a proxy server
Example Usage:
curl -x http://proxy.example.com:8080 example.com
What it does: Routes the request through a specified proxy server.
Command-line Arguments Explained:
-x http://proxy.example.com:8080: Sets the proxy server to use for the request.
Send cookies with a request
Example Usage:
curl -b cookies.txt example.com
What it does:
Includes cookies from the cookies.txt file in the request.
Command-line Arguments Explained:
-b cookies.txt: Sends cookies stored in the specified file with the request.
Retrieve HTTP status code
Example Usage:
curl -w "%{http_code}\n" -o /dev/null -s example.com
What it does: Prints the HTTP status code (e.g., 200, 404) of the response without the body.
Command-line Arguments Explained:
-w "%{http_code}\n": Formats the output to show only the HTTP status code.-o /dev/null: Discards the response body by writing it to/dev/null.-s: Suppresses progress output.
Download a file with the same name
Example Usage:
curl -O http://example.com/file.txt
What it does:
Downloads the file at http://example.com/file.txt and saves it locally with the same name.
Command-line Arguments Explained:
-O: Saves the file using the remote filename.
Upload a file via PUT
Example Usage:
curl -X PUT -d @file.txt http://example.com/upload
What it does:
Uploads the contents of file.txt to the specified URL using the PUT method.
Command-line Arguments Explained:
-X PUT: Specifies the HTTP request method as PUT.-d @file.txt: Reads the request body from the local filefile.txt.
Basic HTTP authentication
Example Usage:
curl -u username:password http://example.com/api
What it does: Sends HTTP Basic Authentication credentials in the request headers.
Command-line Arguments Explained:
-u username:password: Provides the username and password for authentication.
Check connection time (time to first byte)
Example Usage:
curl -w "%{time_connect}\n" -s http://example.com
What it does: Displays the time taken for the TCP connection to be established.
Command-line Arguments Explained:
-w "%{time_connect}\n": Customizes the output to show the time to connect.
Send JSON data in a POST request
Example Usage:
curl -X POST -H "Content-Type: application/json" -d '{"key":"value"}' http://example.com/api
What it does: Sends a JSON payload to an API endpoint with the correct content type.
Command-line Arguments Explained:
-H "Content-Type: application/json": Sets the request header to indicate JSON content.-d '{"key":"value"}': Sends the JSON data in the request body.
Download multiple files
Example Usage:
curl -O http://example.com/file1.txt -O http://example.com/file2.txt
What it does: Downloads multiple files from the specified URLs.
Command-line Arguments Explained:
-O: Saves each file with its remote filename.
Simulate a HEAD request
Example Usage:
curl -X HEAD http://example.com
What it does: Sends a HEAD request to retrieve headers without the response body.
Command-line Arguments Explained:
-X HEAD: Specifies the HTTP request method as HEAD.
Stream output to a file
Example Usage:
curl -OJ http://example.com/file.txt
What it does: Downloads the file and preserves its original filename and content disposition.
Command-line Arguments Explained:
-O: Saves the file with the remote name.-J: Uses the filename from the Content-Disposition header.
Send form-encoded data
Example Usage:
curl -X POST -d "username=admin&password=secret" http://example.com/login
What it does: Submits form data (application/x-www-form-urlencoded) to a login endpoint.
Command-line Arguments Explained:
-d "username=admin&password=secret": Sends form-encoded data in the request body.
Use a specific user agent
Example Usage:
curl -A "MobileUserAgent" example.com
What it does: Sets the User-Agent string to mimic a mobile browser.
Command-line Arguments Explained:
-A "MobileUserAgent": Sets the User-Agent header for the request.
Show verbose output
Example Usage:
curl -v example.com
What it does: Displays detailed information about the request and response, including headers and timing.
Command-line Arguments Explained:
-v: Enables verbose mode for debugging purposes.
Resume a partially downloaded file
Example Usage:
curl -C - -o file.txt http://example.com/file.txt
What it does: Resumes a download from where it left off (useful for large files).
Command-line Arguments Explained:
-C -: Tells curl to resume the download from the last position.
Verify SSL certificate
Example Usage:
curl --cacert /path/to/ca-cert.pem https://example.com
What it does: Verifies the SSL certificate against a specified CA certificate file.
Command-line Arguments Explained:
--cacert /path/to/ca-cert.pem: Specifies the path to a CA certificate file for validation.
Send HTTP/1.1 request
Example Usage:
curl -1 http://example.com
What it does: Forces curl to use HTTP/1.1 instead of the default protocol (usually HTTP/1.1 or HTTP/2).
Command-line Arguments Explained:
-1: Uses HTTP/1.1 protocol.
Send DELETE request
Example Usage:
curl -X DELETE http://example.com/api/resource/123
What it does: Sends a DELETE request to remove a resource at the specified URL.
Command-line Arguments Explained:
-X DELETE: Specifies the HTTP request method as DELETE.
