Mailinglist Archive: opensuse (3397 mails)

[Randall R Schulz <rschulz@xxxxxxxxx>]

Anders,

On Tuesday 26 April 2005 12:19, Anders Johansson wrote:
> On Tuesday 26 April 2005 21:01, Randall R Schulz wrote:
> > Ken,
> >
> > On Tuesday 26 April 2005 11:30, Ken Schneider wrote:
> > > > ...
> > >
> > > umask actually subtracts from what would be full access.
> >
> > Actually, it subtracts from the mode supplied by the program that
> > is issuing the system call to create the file.
>
> Or to be absolutely accurate, it doesn't subtract, it does a logical
> and between the desired permissions and the inversion of the umask

Actually, the term "subtract" _is_ appropriately used here.

A Unix file mode is not really a number, it a concise representation of 
a set. We only use the numeric representation as a convenience (and we 
don't always do that, often preferring a symbolic representation that 
makes the set aspect a little more obvious).

Logicians and mathematicians define the notion of set subtraction. So in 
this context, that sense of "subtract" is correct.


> if you have an umask of 222 and you try to create a file with mode
> 444, that doesn't give you (through subtraction) 222, it gives you
> 444 & 555 = 444.


Randall Schulz