To send form data, a browser will URL-encode it as a series of name=value
pairs separated by ampersand (&) symbols. The resulting string is sent as
the body of a POST request. To do the same with curl, use the -d (or
--data) argument, like this:
curl -d 'name=admin&shoesize=12' http://example.com/
When specifying multiple -d options on the command line, curl will
concatenate them and insert ampersands in between, so the above example could
also be written like this:
curl -d name=admin -d shoesize=12 http://example.com/
If the amount of data to send is too large for a mere string on the command line, you can also read it from a file name in standard curl style:
curl -d @filename http://example.com
While the server might assume that the data is encoded in some special way, curl does not encode or change the data you tell it to send. curl sends exactly the bytes you give it.
To send a POST body that starts with a @ symbol, to avoid that curl tries to
load that as a file name, use --data-raw instead. This option has no file
loading capability:
curl --data-raw '@string' https://example.com