*@*: -> username@hostname:
/home/*/ -> /home/username/
$USER -> username $HOSTNAME -> hostname $LOGNAME -> username
*@*.*[2-4] -> <email address hidden>
*@*: -> username@hostname:
/home/*/ -> /home/username/
$USER -> username
$HOSTNAME -> hostname
$LOGNAME -> username
*@*.*[2-4] -> <email address hidden>