-f, --fail
(HTTP) Fail silently (no output at all) on server errors. This is mostly done to better enable
scripts etc to better deal with failed attempts. In normal cases when an HTTP server fails to
deliver a document, it returns an HTML document stating so (which often also describes why and
more). This flag will prevent curl from outputting that and return error 22.
This method is not fail-safe and there are occasions where non-successful response codes will
slip through, especially when authentication is involved (response codes 401 and 407).
tested and worked with 6.5.1 - Fixes #66
from the curl manpage: