- pathname-expand STRING #!optional BASEprocedure
If STRING is identical to "~" or if it begins with "~/", return the argument with the "~" substituted by the current user's home directory. If the current user cannot be determined or does not exist, a condition of type (exn pathname-expand username) is raised.
If STRING begins with "~USERNAME", return the argument with the "~USERNAME" substituted by the provided user's HOME directory. On Windows, this will be the value of the environment variables USERPROFILE or HOME (or "." if none of the variables is set). On Unix systems, the user database is consulted. If the user does not exist, a condition of type (exn pathname-expand username) is raised.
If STRING is identical to "~~" or if it begins with "~~/", return the argument with the "~~" substituted by (repository-path). If there is no repository path, a condition of type (exn pathname-expand repository-path) is raised.
If STRING doesn't begin with a tilde, and it represents an absolute pathname, then it is returned unchanged. If instead it is a relative pathname the result of (make-pathname STRING BASE) is returned, where BASE defaults to the current working directory.