curl -v --data @payload.txt -H "Content-Type: application/x-www-form-urlencoded" -X POST http://server:8080

where payload.txt contains key-value pairs.

curl can be used to send a compressed HTTP request - HTTP requests are not usually compressed, only the responses are, but the standard does not prohibit setting the Content-Encoding header to gzip, deflate or others and then sending a compressed body.

To send a compressed POST HTTP request, first create a file containing the body that shall be sent, say, request.txt and then compress the file using gzip:

gzip request.txt

For this example, the request.txt file contains POST key-value data such that the request content type will be set to application/x-www-url-form-urlencoded.

The command will create a compressed file request.txt.gz. Afterward, the curl command shall read:

curl -v --data-binary @request.txt.gz "Content-Type: application/x-www-form-urlencoded" -H "Content-Encoding: gzip" -X POST http://server.tld/

where:

• -v turns on verbosity,
• –data-binary @request.txt.gz will send the request.txt.gz file as the request body (mind the @, it is necessary),
• the request Content-Type is set to application/x-www-form-urlencoded indicating that the request.txt.gz file contains POST key-value data,
• the request Content-Encoding is set to gzip,
• the request will be sent to http://server.tld/

Command Line Aspect	Visual Mnemonic Graft
-fLOsS

The following command:

curl -fLOsS https://www.deb-multimedia.org/pool/main/d/deb-multimedia-keyring/deb-multimedia-keyring_2024.9.1_all.deb

will download the binary file deb-multimedia-keyring_2024.9.1_all.deb to the current directory by using fLOsS as command-line parameters passed to curl.

The parameters -fLOsS carry the following meaning:

• -f makes curl fail in case there are errors and to not output any document,
• -L means to follow any redirects,
• -O tells curl to save the the body to the current directory,
• -s makes curl silent,
• -S makes curl show an error in case the download fails (this combines with -s, as in, be silent if no fail)