If the pattern contains wildcard characters, only existing files and directories are returned. Expanding a ‘pattern’ without wildcard characters returns the argument, regardless of whether or not it exists.

Before expanding wildcards, the construct $\arg{var} is expanded to the value of the environment variable var, and a possible leading ~ character is expanded to the user's home directory.^{163On Windows, the home directory is determined as follows: if the environment variable HOME exists, this is used. If the variables HOMEDRIVE and HOMEPATH exist (Windows-NT), these are used. At initialisation, the system will set the environment variable HOME to point to the SWI-Prolog home directory if neither HOME nor HOMEPATH and HOMEDRIVE are defined.}