From: Thomas Demmer <demmer AT LSTM DOT Ruhr-UNI-Bochum DOT De>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: How coould I know if two files are the same?
Date: Fri, 29 Aug 1997 10:39:00 +0200
Organization: Lehrstuhl fuer Stroemungsmechanik
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Eli Zaretskii wrote:
> 
> On Wed, 27 Aug 1997 IBEC23 AT cc DOT uab DOT es wrote:
> 
> > When a network disk drive X:\ is the same as M:\FOLDER,
> > my program "believes" that
> >   X:\FILENAME.TXT
> > is different from
> >   M:\FOLDER\FILENAME.TXT
> > but it is the same file.
> [snip]
> > Is there some way to detect it using DJGPP?
> 
> Yes, use the library function `_truename'.  It should return the
> same canonical string for each of these cases.
> 
> Another way would be to call `stat' on both files and compare the
> st_dev and st_ino members of struct stat: if both of them are
> identical, the two names refer to the same file.
I think this is not correct:
 stat() invents inodes for networked drives, i.e. it
 counts upwards from 65536. It remembers which filenames it has 
 seen before, so that two calls to stat() with the identical
 name yields identical results. In the example above, however, 
 the names are not identical. 


> 
> The second way is more portable (since `stat' is a POSIX function,
> whereas `_truename' was invented for DJGPP), at least if your program
> will need to run on Unix (DOS and MS-Windows compilers usually return
> zero st_ino for all files, since Microsoft filesystems don't have
> inodes).  The call to `stat' is also much more expensive (in DJGPP),
> so if you need to compare hundreds of files, `_truename' would be much
> faster.
What should work is something like

  _fixpath(fn1, fixed_fn1);
  _fixpath(fn2, fixed_fn2);
  _truename(fixed_fn1,canon_path1);
  _truename(fixed_fn2,canon_path2);
  if(!strcmp( canon_path1, canon_path2) ){
   puts("Identical files");
  }

This in fact should work with all network drivers using the Network
Redirector. I'm quite surprised that Xavier wrote in a mail to
me that this didn't work. From (at least) DOS 6.22 command.com has the
built-in command truename, so simply trying
C:>truename m:\folder\filename.txt
should yield something like
\\SERVER\PATH\FOLDER\FILENAME.TXT
and 
C:\>truename x:filename.txt
should give the same. 


-- 
Ciao
Tom

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* Thomas Demmer                                             *
* Lehrstuhl fuer Stroemungsmechanik                         *
* Ruhr-Uni-Bochum                                           *
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