Re: yee-gads! i almost had it.

[Kyle Pointer <kapointer@charter.net>]

Why doesn't someone just ssh into the box already. This is getting far
more confusing than it should be. Not that any information given has
been useless or anything but *I* would find a bunch of binary kinda
intimidating... and I code! I'm not suggesting I do it, because I don't
know crap about permissions but for the love of octagons... Its a flash
drive.. :| It shouldn't be this hard. :(
	--kyle

On Wed, 2005-02-23 at 20:52 -0600, Nathaniel Reindl wrote:
> On Wed, Feb 23, 2005 at 03:07:04PM -0600, bntly.rhds wrote:
> > apparently if i want -rwxrw-r-- then i need to put 764 minus 666 which 
> > gives me 098.  i don't know, but does that sound right?  umask=098 (aka 
> > 764)? 
> 
> You take the complement of the mode you'd set with chmod.  This isn't
> straight-up arthmetic, either; these are logical operations.
> 
> In binary:
> 
> 000 111 110 100 (in octal, 0764, set with chmod)
> 111 000 001 011 (in octal, 7013, set with umask)
> 
> You should notice a pattern here. :)
> 
> FWIW, the modes work like this (with comedy ASCII art option):
> 
>   ___ ___ ___ 
>  /2^2/2^1/2^0/'
> ------------- | 
> | r | w | x | '
> -------------/
> 
> 2^2, if high, sets the permission bit for reading.
> 2^1, if high, sets the permission bit for writing.
> 2^0, if high, sets the permission bit for executing.
> 
> Now, there are four groups (the special group isn't really included
> here, and it's often omitted since there aren't usually special octal
> modes you'd set on files) that comprise a full permission setting.  As
> mentioned already, the group furthest to the left is the special
> group.  The three following that, respectively, are the owner, group,
> and world groups.
> 
> So, the permission set above (0764) would mean that there would be no
> special bits set, the file would be writeable, readable, and
> executable by the owner, the file would be writeable and readable by
> the owning group, and the file would be readable by the world.
> 
> Now, in case anyone is absolutely curious, this isn't the only time
> masks like these are used.  Think about your IP address and subnet
> mask and the relationship between them.  Try ANDing and ORing them. :)
> 

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