Parameter

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.