From owner-freebsd-current  Wed Jun 17 16:13:19 1998
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From: Richard Tobin <richard@cogsci.ed.ac.uk>
Subject: Re: Bogus errno twiddling by lstat... 
To: Warner Losh <imp@village.org>, Terry Lambert <tlambert@primenet.com>
In-Reply-To: Warner Losh's message of Wed, 17 Jun 1998 11:30:21 -0600
Organization: just say no
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> No.  When a system call returns success, the value of errno is
> undefined.

No!  A successful system call leaves it *unchanged*.  From intro(2):

     Successful calls never set errno; once set, it remains
     until another error occurs.

I believe ANSI C has a similar requirement.

You should only examine errno after an error, but you are allowed to have
had intervening successful system calls.

-- Richard

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