Well, I think I may have answered my question already, but
I'll go ahead and post it just to verify myself.
I've been searching various man pages to find out what's the
point of the set-group ID bit on directories.
For instance, consider this directory:
drwxr-sr-x 3 root 512 Nov 8 19:29 etc/
I've been trying to figure out what happens with the 's' bit
set and what doesn't happen. I think I finally found out from
an IBM man page (chmod(2)):
S_ISGID Enables the setgid attribute for an executable file. A
process executing this program acquires the access rights of the
group of the file. Also, enables the group-inheritance attribute
for a directory. Files created in this directory have a group
equal to the group of the directory.
From this, I gather that directories with this bit set change
the group of any files created in them to be of the same group
as the directory itself, rather than of the user making the files.
Why was this information so hard to find? That is, why wasn't it in
the obvious place (chmod(1) or chmod(2)) in the man pages for DEC, Sun,
or HP systems?