19.2.2.4.6 Restrictions on Examining a Pathname Version Component

The version can be any symbol or any integer.

The symbol :newest refers to the largest version number that already exists in the file system when reading, overwriting, appending, superseding, or directory listing an existing file. The symbol :newest refers to the smallest version number greater than any existing version number when creating a new file.

The symbols nil, :unspecific, and :wild have special meanings and restrictions; see Section 19.2.2.2 (Special Pathname Component Values) and Section 19.2.2.5 (Restrictions on Constructing Pathnames).

Other symbols and integers have implementation-defined meaning.