FLAC-Free Lossless Audio Codec

In the linux documentation I don't see any way to compress from the
standard input. I want to convert a bunch of .shn files to flac, with
something like "shn -x filename.shn | flac -" to avoid creating a huge
intermediate wav file on disk. But either there's not a way to do that or
else it's not documented in the man page, so either way a fix would be
great. Thanks.