From the -f description:
(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.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>