‘-q’
‘--quiet’
Turn off Wget's output.
‘-nv’
‘--no-verbose’
Turn off verbose without being completely quiet (use ‘-q’ for
that), which means that error messages and basic information still
get printed.
So there is no way to just get error messages.
Wait. Google says:
"To display only error messages from wget and suppress all other output,
including progress indicators and successful download messages, use the
-nv (no verbose) option in conjunction with redirection of standard
output to /dev/null."
I see. Well please mention that in the manual.