Subj : Re: newbie question [C language]
To   : comp.programming
From : Rob Thorpe
Date : Fri Jul 01 2005 07:14 am

CBFalconer wrote:
> Rob Thorpe wrote:
> > osmium wrote:
> >> "Fred_NacH" writes:
> >>
> >>> I was wondering, how to retrieve the size/length of a file by
> >>> only using the ansi functions...
> >>
> >> This one often causes a lot of controversy, some people say
> >> there is a (usually unnamed) system on which it won't work or at
> >> least there *could have been* a system on which it wouldn't work
> >> if such a system had been built.
> >>
> >> Open the file in *binary* mode, seek to end of file, and use
> >> ftell() to see where you are.  If you like acrimony and pedantry,
> >> look around on Usenet for these discussions which flare up from
> >> time to time.
> >
> > I expect the problem Randy points out is something like a bug -
> > or at least lies in the neverland between bug and feature.
> >
> > fseek to SEEK_END isn't gauranteed to work on a binary file.  I
> > think this is because on some operating systems binary files are
> > made from fixed size block of some number of bytes.  They appear
> > like files in other systems, but with nulls at the end padding
> > out to the end of the block.
> >
> > It's worth pointing out that stat/fstat or a version of it are
> > available on many platforms even though they aren't standard.
>
> Try thinking about device files and sparse files.

I forgot about that.

On some platforms you may be able to get useful information from
stat/fstat.  On others you may get useful information from them on some
volumes or devices, but not others.  On some platforms you may be able
to get it from fseek & ftell.  On others they're may be system specific
interfaces that do the job.

Here be dragons drinking heartly from the blood of the leaking
abstractions.

.