"S" mode for file permission?

[Oleg Cherkasov]

On 12.12.2020 22:08, Peter Flynn wrote:
> On 12/12/2020 17:41, Gary Aitken wrote:
>> I'm having to fix some permissions in some ruby file hierarchies, and
>> came across one with a 'S' for group (note, not 's').  man chmod doesn't
>> mention 'S', although it does mention 'X'.  Can someone tell me what 'S'
>> represents, and why an attempt to chmod g+s results in a 'S'?  Also, why
>> it would be set that way for a particular directory when all others above
>> it have 's'?
> 
> S(s) sets the Sticky Bit. https://en.wikipedia.org/wiki/Sticky_bit

I always thought the Sticky Bit is rather T(t).  The mentioned wikipage 
confirms it, scroll to examples at the bottom.