user-homedir-pathname &optional host → pathname
host — a string, a list of strings, or :unspecific.
pathname — a pathname, or nil.
user-homedir-pathname determines the pathname that corresponds to the user’s home directory on host. If host is not supplied, its value is implementation-dependent. For a description of :unspecific, see Section 19.2.1 (Pathname Components).
The definition of home directory is implementation-dependent, but defined in Common Lisp to mean the directory where the user keeps personal files such as initialization files and mail.
user-homedir-pathname returns a pathname without any name, type, or version component (those components are all nil) for the user’s home directory on host.
If it is impossible to determine the user’s home directory on host, then nil is returned. user-homedir-pathname never returns nil if host is not supplied.
(pathnamep (user-homedir-pathname)) → true
The host computer’s file system, and the implementation.