user-homedir-pathname

(user-homedir-pathname &optional host)

Returns the user's home directory as a directory pathname -- the namestring always ends in a separator, and the name and type components are nil. The value comes from the HOME environment variable; the host argument is accepted and ignored, since there is one host.

nil when HOME is unset, which Common Lisp allows and is the honest answer on a WASI guest that was given no environment at all.

$ rontolisp -e '(print (user-homedir-pathname))'
#P"/home/you/"

Backend support

Works on all four backends: one definition in rontolisp source over the per-backend environment primitive.