GNU bug report logs - #19969
problem: wc -c doesn't read actual # of bytes in file

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Message #17 received at 19969 <at> debbugs.gnu.org (full text, mbox):

From: Mike Frysinger <vapier <at> gentoo.org>
To: Eric Blake <eblake <at> redhat.com>
Cc: Linda Walsh <coreutils <at> tlinx.org>, 19969 <at> debbugs.gnu.org
Subject: Re: bug#19969: problem: wc -c doesn't read actual # of bytes in file
Date: Mon, 2 Mar 2015 11:59:20 -0500

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On 02 Mar 2015 06:57, Eric Blake wrote:
> On 02/28/2015 01:59 AM, Linda Walsh wrote:
> > (coreutils-8.21-7.7.7)
> > 
> > wc -c(bytes) doesn't seem to reliably read the number
> > of bytes in a file.
> > 
> > I was wanting to find out what the largest data-source
> > files in '/proc' and '/sys' (didn't get around to trying
> > /sys, since all the files under /proc/sys return 0 bytes.
> 
> The Linux kernel is notoriously bad about advertising 0-length file size
> for non-empty contents of files within sysfs and procfs.  Any program
> that trusts just stat() output will report 0; the only way to see
> non-zero sizes on these special files is to open() and read() them (I'm
> not even sure if lseek(SEEK_END) does the trick) - but fixing that is
> something for the kernel folks to do, and not coreutils to work around,
> because it is more than coreutils that is affected by the kernel's lies.

to be fair, for some pseudo files, it's not feasible or possible to report the 
real size

`wc -c < /proc/file` should work
-mike

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