Working with DOS

DOS filenames

DOS filenames can be 255 characters long and can contain characters from the Unicode Character set, including lower case letters and those that are not in IBM PC Extended ASCII, like the Euro character (0x20ac). Filenames can also have spaces. They cannot, however, start with a dot (.) and cannot contain the following special characters:

   "  / : * < > | ?

NOTE: Note that although filenames can contain lowercase letters (unlike filenames in the FAT12 and FAT16 versions of the DOS FSType supported in earlier releases of UnixWare), the VFAT and FAT32 versions of the DOS filesystem introduced in the current release of UnixWare are still not case sensitive. This means that the filenames ABC, abc, and Abc all refer to the same file in a DOS filesystem. UnixWare support for lowercase letters only helps in preserving the case of filenames for display purposes.

Traditional 8.3 DOS filenames (an 8 character name portion and a 3 character extension) are known as ``short names'' in a VFAT DOS filesystem. Filenames that can't be represented in the traditional 8.3 style are known as ``long names''. These include filenames that include:

lowercase letters
any of these characters: ``[ ] + = ; ,''
spaces
more than one dot (``.'')
a name portion longer than 8 characters, or an extension portion longer than 3 characters (the rightmost dot separates the name from the extension)

A long filename has a corresponding alias name, derived from the long name and meeting all the requirements of traditional 8.3 style DOS filenames. On Windows systems a file can be accessed by its long name or its alias name. On UnixWare the alias name is internal to the system: it exists only so that old applications can see the file.

The three letter extension in traditional DOS filenames indicates if a file is executable (DOS does not provide an equivalent to the ``executable'' permission bit). Files ending in .EXE, .SYS or .COM are programs, and files ending in .BAT are batch (script) files.

If you create a file on a UnixWare system and transfer it to a DOS system, avoid giving it one of these extensions. Otherwise, DOS may mistake it for an executable program, with unpredictable results.