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From: ralf@b.gp.cs.cmu.edu (Ralf Brown)
Newsgroups: comp.os.msdos.programmer
Subject: Re: "file cannot be copied onto itself"
Message-ID: <10478@pt.cs.cmu.edu>
Date: 15 Sep 90 02:47:26 GMT
References: <2091@nyx.UUCP>
Organization: Carnegie-Mellon University, CS/RI
Lines: 41

In article <2091@nyx.UUCP> cla@nyx.UUCP () writes:
}How does one determine that two files are indeed the same physical file?

Under DOS 3.0 and up, the easiest way is to apply the following undocumented
function to both names and then do a string compare.

INT 21 - DOS 3+ internal - RESOLVE PATH STRING TO CANONICAL PATH STRING
        AH = 60h
        DS:SI -> ASCIZ relative path string or directory name
        ES:DI -> 128-byte buffer for ASCIZ canonical fully qualified name
Return: CF set on error
            AX = error code
                02h invalid source name
                03h invalid drive or malformed path
                others???
        CF clear if successful
            AH = 00h
            AL = destroyed (00h or 5Ch or last char of current dir on drive)
            buffer filled with qualified name of form D:\PATH\FILE.EXT or
              \\MACHINE\PATH\FILE.EXT
Notes:  the input path need not actually exist
        letters are uppercased, forward slashes converted to backslashes,
          asterisks converted to appropriate number of question marks, and
          file and directory names are truncated to 8.3 if necessary.
        '.' and '..' in the path are resolved
        filespecs on local drives always start with "d:", those on network
          drives always start with "\\"
        if path string is on a JOINed drive, the returned name is the one that
          would be needed if the drive were not JOINed; similarly for a
          SUBSTed, ASSIGNed, or network drive letter.   Because of this, it is
          possible to get a qualified name that is not legal under the current
          combination of SUBSTs, ASSIGNs, JOINs, and network redirections
        functions which take pathnames require canonical paths if invoked via
          INT 21/AX=5D00h
        supported by OS/2 v1.1 compatibility box
SeeAlso: INT 2F/AX=1123h,1221h
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