On Tue, Aug 16, 2011, Stefan Johnson wrote: > On most of the unix / unix-like systems I support, this behavior would be > different. The file would be created with user_a:group_a (since group_a is > the primary group.) This is true on AIX, Solaris, Linux, and HP-UX per my > testing earlier today. On Tru64 and OpenBSD, the group ownership seems > to be inherited by the parent directory rather than set by the user's > primary group > membership. For AIX et.al. the "setgid" bit on the parent directory would > change > the behavior such that files created inside that directory would be owned by > the > parent directory group owner regardless of user's primary group membership. > > It appears that OpenBSD (and Tru64) treat the directory as setgid (when > compared to the other OSes) but it is not.
BSD derived systems always have the setgid directory behavior. The rationale is that if you have users sharing a directory, this is the behavior you want and you shouldn't need to remember to chmod every directory created, especially since you may not be creating directories by hand.
