On Sat, Nov 1, 2014, at 18:01, Michael Forney wrote: > It looks like GNU tar does¹, but BSD tar uses the string > representation of the UID/GID. > > ¹ http://git.savannah.gnu.org/cgit/tar.git/tree/src/names.c#n66
I didn't think to look at a modern BSD (the relevant function is name_uid in pax/cache.c). Either way, any tar should be able to cope with either output, assuming no system has the pathological case of a user account with a numeric name different from its uid, but a blank string seems to be more POSIX-correct. There's another tar (possibly actually called bsdtar) in contrib/libarchive that I couldn't make heads or tails of (it uses some kind of modular design and I couldn't find the real implementation of everything)
