Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!pt.cs.cmu.edu!b.gp.cs.cmu.edu!Ralf.Brown@B.GP.CS.CMU.EDU
From: Ralf.Brown@B.GP.CS.CMU.EDU
Newsgroups: comp.sys.ibm.pc
Subject: Re: Symbolic links in DOS (a la Unix) ?
Message-ID: <24d97d89@ralf>
Date: 4 Aug 89 11:27:05 GMT
Sender: ralf@b.gp.cs.cmu.edu
Organization: Carnegie Mellon University School of Computer Science
Lines: 36
In-Reply-To: <1583@unccvax.UUCP>

In article <1583@unccvax.UUCP>, cs75jmc@unccvax.UUCP (John Covington WN4BBJ) wrote:
}In article <5569@arcturus>, mitch@arcturus.UUCP (Mitchell S. Gorman) writes:
}>       What problems would occur if one should attempt to implement a
}> unix-like symbolic link to directories by creating an entry in a directory
}> that has a FAT start-point that is the same as a "real" directory somewhere
}> else in the tree?  
}
}Consider this:  You create two subdirectory entries  and zap them so
}they point to the same cluster.  You then copy 300 files into the one
}called \TEST.  A normal subdirectory starts out holding something like
}144 files and is extended to accomodate additional files.  The length of
}\TEST as stored in the root directory will be increased, but \REAL will
}not be modified.  What will DOS do then when you access \REAL? Will it 
}follow the FAT chain to determine the length of \REAL or will it go as 
}far as the root directory entry says it can go?

As it happens, the length of a directory as reported in ITS directory entry
is always zero.  The true length is determined by following the FAT chain,
except for the root directory, which is always of fixed size.

}I am sure this would work only as long as you don't dump over 144 files
}into the subdirectory; otherwise some strange things are likely to
}happen.

Directory entries are 32 bytes, so 2K clusters allow 64 entries, 4K clusters
allow 128 entries, etc., before another cluster has to be added.  Don't forget
to count '.' and '..' as entries.
--
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FAX: available on request                      Disclaimer? I claimed something?

Alan Demers: Here is the promised Fast Fourier Transform example.  It worked
         for the two examples I tried, so I'm fairly sure it is correct.
Student: Proof by exhaustive testing?
Demers:  Well, it sure exhausted me.