Int 21H, AH=60H

3 and higher

TRUENAME - CANONICALIZE FILENAME OR PATH

AH = 60h
DS:SI -> ASCIZ filename or path
ES:DI -> 128-byte buffer for canonicalized name

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

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

AX=5F02h - AX=7160h/CL=00h - INT 2F/

Text based on Ralf Brown Interrupt List Release 61