linux-kernel - Re: Behavior of lseek() on a fd opened with 'RDONLY' flag, when seeking goes beyond file size.

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Date:	Sun, 22 Jun 2008 11:36:12 +0930
From:	David Newall <davidn@...idnewall.com>
To:	palani saravanan <busybeesaravanan0072003@...oo.co.in>
CC:	linux-kernel@...r.kernel.org
Subject: Re: Behavior of lseek() on a fd opened with 'RDONLY' flag, when seeking
 goes beyond file size.

palani saravanan wrote:
> Does lseek() permits -ve value as offset, with SEEK_SET mode? ...
>    errno = 0;
>    rd_rc = lseek(rd_fd, -10, SEEK_SET);
> returns rd_rc = -10 and errno remains 0.
>   

No, lseek does not permit negative file offsets, and should return
EINVAL in your example.  You may have discovered a bug.  For reference,
on my system lseek returns -1 and sets errno to EINVAL, as it should.

If you're running a recent kernel it might be worth looking closer into
this; for older kernels it's probably not worth the effort.
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