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

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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.

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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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