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

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Message-ID: <4857CA71.3020004@davidnewall.com>
Date:	Wed, 18 Jun 2008 00:00:09 +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:
>    In linux, I see that it just goes beyond the file size and returns the resulting offset.
>    For example, 'rc = lseek(fd, 4L, SEEK_END);' on a file which has 5 byte contents,
>    it returns rc as 9.
>   

Sounds right.  It's documented that way, too:

       "The lseek() function allows the file offset to be set beyond the
end of  the  file  (but  this
       does  not  change  the  size of the file)."
           -- man 2 lseek
>    I expect that it would return size of the file, i.e.) 5.
>   

Only if you pass (0,SEEK_END).

>    Does the file pointer internally really points to the new location.?
>   

So the documentation promises.
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