Calculate the resulting permission bits and behavior of setting the SGID bit on files or directories.
The SGID (Set Group ID) bit, 2000 in octal special-permissions notation, behaves differently depending on what it's applied to: on a directory, it makes every new file and subdirectory created within automatically inherit the parent directory's group ownership rather than the creating user's primary group — the standard mechanism for shared team directories where multiple users need consistent group-level access to files others create. On an executable file, it works like SUID but for group privileges: the process runs with the file's group ownership rather than the invoking user's group, a less common pattern than directory SGID but still used by some system tools (e.g. `wall`, `write` historically use group-based SGID for tty access).
SGID in octal notation
2000 = SGID bit; full mode = 2000 + owner/group/other permission bits (e.g. 2775)
`chmod g+s /shared/dir` (or `chmod 2775 /shared/dir`) combined with setting the directory's group ownership (`chown :teamgroup /shared/dir`) ensures every file subsequently created inside inherits the teamgroup group, keeping collaborative access consistent without users needing to manually chgrp every new file.
`find / -perm -2000 2>/dev/null` lists every file or directory with the SGID bit set — combine with `-type d` or `-type f` to filter specifically for directories or files.
No — SGID must be set explicitly on each directory where inheritance is wanted; new subdirectories created inside an SGID directory do inherit the SGID bit itself (so the behavior propagates), but pre-existing subdirectories created before SGID was set do not retroactively gain it.