mixed File_Passwd_Common::listUser ( 
    string $user = ''
   )
List one user's properties or all users.
$user
     the user to list or all users if empty
Returns array of user(s) or PEAR_Error on failure.
| Error Code | Summary | 
|---|---|
| FILE_PASSWD_E_NOT_EXISTS | suer doesn't exist | 
This function can not be called statically.