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INT 21 - DOS 3.0+ - "TRUENAME" - CANONICALIZE FILENAME OR PATH
AH = 60h
DS:SI -> ASCIZ filename or path
ES: DI -> 128-byte buffer for canonicalized name
Return: CF set on error
AX = error code
02h invalid component in directory path or drive letter only
03h malformed path or invalid drive letter
ES: DI buffer unchanged
CF clear if successful
AH = 00h or 3Ah (DOS 6.1/6.2 for character device)
AL = destroyed (00h or 2Fh or 5Ch or last character of current
directory on drive)
buffer filled with qualified name of form D:\PATH\FILE.EXT or
\\MACHINE\PATH\FILE.EXT
Desc: determine the canonical name of the specified filename or path,
corresponding to the undocumented TRUENAME command in COMMAND.COM
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. (DR DOS
3.41 and 5.0 do not expand asterisks)
'.' 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
under DOS 3.3 through 6.00, a device name is translated differently if
the device name does not have an explicit directory or the directory
is \DEV (relative directory DEV from the root directory works
correctly). In these cases, the returned string consists of the
unchanged device name and extension appended to the string X:/
(forward slash instead of backward slash as in all other cases) where
X is the default or explicit drive letter.
under MS-DOS 7.0, this call returns the short name for any
long-filename portions of the provided pathname or filename
functions which take pathnames require canonical paths if invoked via
INT 21/AX=5D00h
supported by OS/2 v1.1 compatibility box
NetWare 2.1x does not support characters with the high bit set; early
versions of NetWare 386 support such characters except in this call.
In addition, NetWare returns error code 3 for the path "X:\"; one
should use "X:\." instead.
Novell DOS 7 reportedly has difficulty with non-MS-DOS filenames on
network drives, and can return "D:" instead of "SERVER/VOLUME"
for DOS 3.3-6.0, the input and output buffers may be the same, as the
canonicalized name is built in an internal buffer and copied to the
specified output buffer as the very last step
for DR DOS 6.0, this function is not automatically called when on a
network. Device drivers reportedly cannot make this call from their
INIT function. Using the same pointer for both input and output
buffers is not supported in the April 1992 and earlier versions of
DR DOS
Windows for Workgroups 3.11, Windows95 and even MS-DOS 7.00 only
return the local drive path; to obtain network paths use
INT 21/AX=5F02h or INT 21/AX=5F46h instead
Corel's CORELCDX and MSCDEX without the /S switch return canonical
names of the form "\\D.\A.\path", where "D" is the CD-ROM drive
letter and "A" appears to indicate the first physical CD-ROM drive;
MSCDEX with the /S switch returns a canonical name with embedded
blanks. Novell DOS 7 NWCDEX as of the 11/16/94 update returns the
same canonical path as MSCDEX; earlier revisions returned
"Cdex. D:\path", where "D" is the CD-ROM drive letter
the Windows95 MSCDEX-replacement VxD returns "D:\path", even though the
MS-DOS 7.00 MSCDEX behaves identically to older versions (above)
BUG: Windows95 incorrectly treats filenames where the first two characters
after the drive letter and colon are both slashes (either forward
or backward) as a UNC (network name) and requires several seconds
to attempt to resolve the name before returning an unchanged
string