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Date: Thu, 14 Apr 2016 10:36:37 +0100
From: "Richard W.M. Jones" <rjones@redhat.com>
To: corbet@lwn.net
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Subject: Re: [PATCH] procfs: expose umask in /proc/<PID>/status (formerly
 umask2, formerly getumask)
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On Thu, Apr 14, 2016 at 10:34:48AM +0100, Richard W.M. Jones wrote:
> It's not possible to read the process umask without also modifying it,
> which is what umask(2) does.  A library cannot read umask safely,
> especially if the main program might be multithreaded.
> 
> Add a new status line ("Umask") in /proc/<PID>/status.  It contains
> the file mode creation mask (umask) in octal.  It is only shown for
> tasks which have task->fs.
> 
> For the library this allows me to read the umask from
> /proc/self/status.
> 
> This patch is adapted from one originally written by Pierre Carrier:
> https://lkml.org/lkml/2012/5/4/451

Sorry, I meant to add an example of what this looks like:

$ grep Umask /proc/1/status 
Umask:	  022
$ grep Umask /proc/2/status 
Umask:	  022
$ grep Umask /proc/self/status 
Umask:	  022
$ umask 002
$ grep Umask /proc/self/status 
Umask:	  02

Rich.

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