From:	Hans-Bernhard Broeker <broeker AT physik DOT rwth-aachen DOT de>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: filelength(): POSIX or not
Date:	31 Oct 2000 18:53:10 GMT
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Damian Yerrick <Bullcr_pd_yerrick AT hotmail DOT comremovebullcr_p> wrote:

> fopen() the file in "rb" mode, fseek() to the end, and read the
> length with ftell().  This is ANSI so it should work on any full
> ANSI C compiler.

The calling sequence is ANSI, right. But it's not at all ANSI to
assume it will always do what you think it does. To quote the C
standard on this:

[ISO-C 89:7.9.9.2#2, C99 draft 7.19.9.2#2]:

       A binary stream
       need not meaningfully support  fseek  calls  with  a  whence
       value of SEEK_END.

It's long-standing knowledge in the C newsgroups there is, in fact, no
way at all to portably find the length of a given file other than
reading all of it and adding the byte counts.
-- 
Hans-Bernhard Broeker (broeker AT physik DOT rwth-aachen DOT de)
Even if all the snow were burnt, ashes would remain.

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