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Special Usage (overloading) of Permission Bits on various Unix flavours

This is about overloading of

S_ISUID   04000 set user ID on execution
S_ISGID   02000 set group ID on execution
S_ISVTX   01000 sticky bit
If so, it should be documented in chmod(2).

The sticky bit in /tmp is well known.
But then I heard of more special meanings and became curious.

By the way: did you know that the setuid bit has been patented? By Dennis M. Ritchie himself. Pt. no 4135240.
See f.i. the USPTO search and search for this number, or see google patents/US4135240.

2015-05-01 (see recent changes)


1. Files

set uid (without execute by user)

set gid (without execute by group)

sticky bit


2. Directories

set uid

set gid

sticky bit


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