What are negative permissions?

Matthew Seaman matthew at FreeBSD.org
Sun Sep 16 19:38:10 UTC 2012

On 16/09/2012 19:57, Gary Aitken wrote:
> Can someone explainn to me what "negative group permissions" are?

It's where the group ownership of a file gives it fewer permissions than
are allowed for the world in general.

Suppose you have a file with these permissions and ownership:

foo bar -rwx---r-x

The owner -- foo -- has full read, write and execute permissions on the
file.  Anyone has read and execute permissions.  But the group -- bar --
has no permissions.

Now, logically, you might think that the world permissions would
override the lack of group permissions, but in fact, that's not what
happens.  Permissions like that mean 'everyone *except* members of group
bar can read and execute this.



Dr Matthew J Seaman MA, D.Phil.
PGP: http://www.infracaninophile.co.uk/pgpkey

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