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.^{146On 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.}