The -fi is an output option that
does not write. It is used to terminate a -if
or a -not_if section when you don't want to
execute an output operation.
$ wgrib2 bad.grb -if ":LHTFL:" -rpn "-1:*" -fi -grib fixed.grb
The above example changes the sign of the LHTFL fields and then
writes the revised data to fixed.grb.