Uppercase S in permissions of a folder

Question

What does the letter S mean below? The file in question is a folder.

                                                               

I read here that an upper-case S can represent that the setgid bit is active for a binary executable. But this is a folder. Does it still mean that the setgid bit is activated for it? If so, what does that mean?

Answer 1

That mean that any file dropped into the folder will take on the folder's owning group.

For example - suppose you have a folder called "shared" which belongs to user "intrpc" and group "users", and you drop a file into it, the copy will be belong to "intrpc" and "users" .

On most systems, if a directory's set-group-ID bit is set, newly created subfiles inherit the same group as the directory, and newly created subdirectories inherit the set-group-ID bit of the parent directory.

you can read about it here.

Why is it upper-cased (from the link you gave) ?

setgid has no effect if the group does not have execute permissions. setgid is represented with a lower-case "s" in the output of ls. In cases where it has no effect it is represented with an upper-case "S".

Answer 2

The upper case S is because the directory does not have execute permissions for the group. In a way this indicates an "error", as you are saying:

newly created subfiles inherit the same group as the directory, and newly created subdirectories inherit the set-group-ID bit of the parent directory.

However, you are denying permission for the group members to enter the directory.