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Date: Fri, 27 Mar 2009 21:19:53 +0100 (CET)
From: "Joost Bekkers" <joost@jodocus.org>
To: "Tobias Rehbein" <tobias.rehbein@web.de>
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Cc: freebsd-questions@freebsd.org
Subject: Re: [perl] sysopen(CD, "/dev/cd0", O_RDONLY | O_NONBLOCK) fails
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On Fri, March 27, 2009 19:59, Tobias Rehbein wrote:
> Am Thu, Mar 26, 2009 at 10:11:28PM +0000 schrieb Bruce Cran:
>>
> Hm. Tried this and got ineresting results:
>
>> use POSIX;
>> sysopen(CD,"/dev/cd0", O_RDONLY|O_NONBLOCK) || perror("sysopen")
> works fine, but
>> use POSIX;
>> sysopen(CD,"/dev/cd0", O_RDONLY|O_NONBLOCK)
>> print "$!"
> prints "No such file or directory"
>
> Well, I think I'll have to accept that sysopen works but $! does not...
> After
> all sysopen is more important to me ;)

As the perlvar manpage tells us:

  $!      If used numerically, yields the current value of the C "errno"
          variable, or in other words, if a system or library call fails,
          it sets this variable.  This means that the value of $! is
          meaningful only immediately after a failure.

The value of $! is NOT an indicator of success or failure. It only tells
you why something failed. If something succeeded $! is usualy left
untouched.


Joost.