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Re: how can i find the size of a binary file

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James Kuyper <jameskuyper@verizon.net> writes:
> On 11/11/2011 04:53 PM, mark wrote:
> >> In <j9k4i8$tah$1@speranza.aioe.org> mark <nospam@nospam.com> writes:
> >>
> >>> thanks for any help
> >>
> >> Call fread() in a loop and keep track of how many total bytes were read.
> > 
> > thanks for ur answer but this will b very inefficent, my question is - 
> > what is the builtin filesize function in c
> 
> There isn't one. That was considered to be too OS-dependent to justify
> standardizing it. For example, on some operating systems, the only thing
> that you can quickly determine is how much space has been allocated to
> store a file; how much of that space has actually been used can only be
> determined by some procedure equivalent to the fread() method given
> above. POSIX provides stat(), lstat(), and fstat(); other OSs provide
> other methods.
> 
> One approach that works on many systems is fseek(file, 0, SEEK_END)
> followed by ftell(file). However, make sure to check for an error return
> from fseek() - "A binary stream need not meaningfully support fseek
> calls with a whence value of SEEK_END." (7.19.9.2p3).
> 
> An extended discussion started the last time someone asked something
> like this. A popular contention was that it's pointless to ask how big a
> file is, because at best, the answer you'll get is how big it was at
> some time in the past; it might be a different size now. That point of
> view has some validity, but it ignores two things:
> 
> 1. You might be explicitly looking for the current value of a time
> dependent quantity, such as keeping track of how fast a file is growing.
> 
> 2. You might have done something to make sure that the file shouldn't
> change in size. This is extremely common, in my experience. There's
> often only one unprivileged userid currently authorized to change a
> given file. If that userid is mine, it's reasonably safe to assume that
> if I'm not currently changing the file, it's size won't change.

And some day in the future someone might even invent read-only media, 
such that it's physically impossible for the file, and thus its size,
to be changed.

Phil
-- 
Unix is simple. It just takes a genius to understand its simplicity
-- Dennis Ritchie (1941-2011), Unix Co-Creator

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how can i find the size of a binary file mark <nospam@nospam.com> - 2011-11-11 21:37 +0000
  Re: how can i find the size of a binary file John Gordon <gordon@panix.com> - 2011-11-11 21:48 +0000
    Re: how can i find the size of a binary file mark <nospam@nospam.com> - 2011-11-11 21:53 +0000
      Re: how can i find the size of a binary file jacob navia <jacob@spamsink.net> - 2011-11-11 23:00 +0100
      Re: how can i find the size of a binary file James Kuyper <jameskuyper@verizon.net> - 2011-11-11 17:20 -0500
        Re: how can i find the size of a binary file Keith Thompson <kst-u@mib.org> - 2011-11-11 15:15 -0800
        Re: how can i find the size of a binary file Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2011-11-12 12:43 +0200
      Re: how can i find the size of a binary file Keith Thompson <kst-u@mib.org> - 2011-11-11 14:25 -0800
  Re: how can i find the size of a binary file jacob navia <jacob@spamsink.net> - 2011-11-11 22:59 +0100
    Re: how can i find the size of a binary file Barry Schwarz <schwarzb@dqel.com> - 2011-11-11 17:46 -0800
      Re: how can i find the size of a binary file "io_x" <a@b.c.invalid> - 2011-11-14 18:18 +0100
        Re: how can i find the size of a binary file Barry Schwarz <schwarzb@dqel.com> - 2011-11-14 20:55 -0800
  Re: how can i find the size of a binary file Keith Thompson <kst-u@mib.org> - 2011-11-11 14:03 -0800
    Re: how can i find the size of a binary file Barry Schwarz <schwarzb@dqel.com> - 2011-11-11 17:46 -0800
      Re: how can i find the size of a binary file Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-11-14 01:21 -0800
        Re: how can i find the size of a binary file Barry Schwarz <schwarzb@dqel.com> - 2011-11-14 20:55 -0800
          Re: how can i find the size of a binary file Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-11-15 00:41 -0800
            Re: how can i find the size of a binary file James Kuyper <jameskuyper@verizon.net> - 2011-11-15 06:53 -0500
    Re: how can i find the size of a binary file Vincenzo Mercuri <vincenzo.mercuri@yahoo.it> - 2011-11-13 02:23 +0100
    Re: how can i find the size of a binary file Nobody <nobody@nowhere.com> - 2011-11-13 02:47 +0000
      Re: how can i find the size of a binary file jacob navia <jacob@spamsink.net> - 2011-11-13 08:44 +0100
        Re: how can i find the size of a binary file Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-11-13 12:31 +0000
        Re: how can i find the size of a binary file Roberto Waltman <usenet@rwaltman.com> - 2011-11-13 10:31 -0500
        Re: how can i find the size of a binary file Nobody <nobody@nowhere.com> - 2011-11-19 07:37 +0000
          Re: how can i find the size of a binary file Kaz Kylheku <kaz@kylheku.com> - 2011-11-19 17:54 +0000
            Re: how can i find the size of a binary file Willem <willem@toad.stack.nl> - 2011-11-19 18:18 +0000
            Re: how can i find the size of a binary file Keith Thompson <kst-u@mib.org> - 2011-11-19 14:19 -0800
              Re: how can i find the size of a binary file Kaz Kylheku <kaz@kylheku.com> - 2011-11-20 01:14 +0000
                Re: how can i find the size of a binary file Keith Thompson <kst-u@mib.org> - 2011-11-19 21:41 -0800
                Re: how can i find the size of a binary file Kaz Kylheku <kaz@kylheku.com> - 2011-11-20 05:52 +0000
                Re: how can i find the size of a binary file Keith Thompson <kst-u@mib.org> - 2011-11-19 22:23 -0800
        Re: how can i find the size of a binary file David Thompson <dave.thompson2@verizon.net> - 2011-11-21 02:39 -0500
  Re: how can i find the size of a binary file blp@cs.stanford.edu (Ben Pfaff) - 2011-11-11 14:32 -0800
    Re: how can i find the size of a binary file Barry Schwarz <schwarzb@dqel.com> - 2011-11-11 17:46 -0800
  Re: how can i find the size of a binary file Ike Naar <ike@sverige.freeshell.org> - 2011-11-11 22:41 +0000
  Re: how can i find the size of a binary file "BartC" <bc@freeuk.com> - 2011-11-13 12:32 +0000
    Re: how can i find the size of a binary file "BartC" <bc@freeuk.com> - 2011-11-13 14:56 +0000

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