DOS Fn 5aH: Create Unique Temporary File

                                                         Compatibility: 3.0+ 
 Expects: AH    5aH
          DS:DX address of ASCIIZ▲ path (i.e., d:\path\0)
          CX    file attribute
          ──────────────────────────────────────────────────────────────────
 Returns: AX    error code if CF is set to CY
                file handle (if no error)
          DS:DX (+n) filename has been appended to path
          ──────────────────────────────────────────────────────────────────
    Info: Creates (opens) a file with a unique filename in a specified
          directory and returns a handle to that file and its full name.
          The DOS command processor uses this function to create the
          temporary "piping" files used in I/O redirection.

          The pathspec must be ready to receive a filename at its end; that
          is, the last character must be a backslash (\) and you must
          provide at least 12 bytes at the end of the string.  In summary,
          it must be in the form:

            "d:\path\",0  (specify drive and path)       ...OR...
            "d:",0        (default directory of a drive) ...OR...
            "d:\",0       (root directory of a drive)    ...OR...
            "",0          (default drive and directory)

          Upon return, the string at DS:DX has a unique filename appended
          to it and the file is open for read/write Access Mode.

   Notes: ■ DOS builds a filename of hex digits obtained from the current
            system date/time.  If the filename already exists, DOS keeps
            trying new names until a file can be created.

          ■ The files created ARE NOT really TEMPORARY, and must be deleted
            via Fn 41H if you don't want them to clutter up your
            directories.

          ■ It is good practice to check the environment for a variable
            named TEMP and use its value as the directory for the file.

See Also: Handle-Oriented File I/O
          DOS Functions
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