[Haskell-cafe] Re: ANNOUNCE: New versions of ALL the monadic regions packages

Brandon S. Allbery KF8NH allbery at ece.cmu.edu
Fri Jan 8 00:03:51 EST 2010

On Jan 7, 2010, at 14:44 , Bas van Dijk wrote:
> On Thu, Jan 7, 2010 at 5:18 PM, Bulat Ziganshin
> <bulat.ziganshin at gmail.com> wrote:
>> Thursday, January 7, 2010, 6:25:34 PM, you wrote:
>>> So now I'm confused... are these standard file handles always open  
>>> on
>>> program startup or are there abnormal situations when they are  
>>> closed?
>> afaik, parent process may close them before executing your program,
>> it's used in particular for running daemons
> Thanks Bulat for explaining.

POSIX actually discourages that, because it's so common for library  
routines to assume they can write error messages to stderr; the  
approved way to handle daemons is to open the standard file handles  
on /dev/null, *not* to close them.  There are systems that violate  
this, however (the most "fun" one I've encountered is Applications  
menu commands in Mac OS X 10.4's X11.app; bash partially works around  
it, but not entirely).

So the correct thing to do is to check if they are open on startup,  
and if not open /dev/null.

brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allbery at kf8nh.com
system administrator [openafs,heimdal,too many hats] allbery at ece.cmu.edu
electrical and computer engineering, carnegie mellon university    KF8NH

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