/sys$common/syshlp/helplib.hlb SHOW, USERS, Parameter  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 username

    Specifies the user about whom you want information. The asterisk
    (*)  and the percent sign (%) wildcard characters are allowed.
    If you specify a string, all users whose user names begin with
    the string are displayed. For example, if you specify the string
    MAR, all user names that begin with MAR are displayed. If no user
    exists whose name matches the specified string, an informational
    message tells you that no processes were found.

    If you omit the username parameter, a list of all interactive,
    subprocess, and batch users is displayed.