To send form data, a browser URL encodes 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 concatenates
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 filename 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 (except that when reading from a file. -d
skips over the carriage returns and newlines so you need to use
--data-binary if you rather intend them to be included in the data.).
To send a POST body that starts with a @ symbol, to avoid that curl tries to
load that as a filename, use --data-raw instead. This option has no file
loading capability:
curl --data-raw '@string' https://example.com