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

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Date:	Mon, 23 Jun 2008 14:08:49 +0530 (IST)
From:	palani saravanan <busybeesaravanan0072003@...oo.co.in>
To:	David Newall <davidn@...idnewall.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Behavior of lseek() on a fd opened with 'RDONLY' flag, when seeking goes beyond file size.

Thanks David for clarification !

I ran this program in the kernel version, 'Linux 2.6.9-42.7.ELsmp'.
However, In a recent kernel version,  'Linux 2.6.24-19 ', the error EINVAL is returned as you mentioned.

Thanks,
Saravanan
----- Original Message ----
From: David Newall <davidn@...idnewall.com>
To: palani saravanan <busybeesaravanan0072003@...oo.co.in>
Cc: linux-kernel@...r.kernel.org
Sent: Sunday, 22 June, 2008 7:36:12 AM
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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