who

查看当前系统中当前登录的帐户

$who
jiang    :0           2016-10-13 08:55 (:0)
jiang    pts/4        2016-10-13 09:03 (:0)
jiang    pts/1        2016-10-13 09:00 (:0)
jiang    pts/6        2016-10-13 09:59 (:0)

如果在tty7里$su，那么$who不会识别root，需要在tty1里登录$su root，就可以在任何终端里执行$who查看到root用户

$su
# who
jiang    :0           2016-10-13 08:55 (:0)
jiang    pts/1        2016-10-13 10:01 (:0)

#切换到tty1里登录root
$su
#再切换回来
# who
jiang    :0           2016-10-13 08:55 (:0)
root     tty1         2016-10-13 14:44
jiang    pts/1        2016-10-13 10:01 (:0)

#切换到tty1里退出root
$exit
#再切换回来
# who
jiang    :0           2016-10-13 08:55 (:0)
jiang    pts/1        2016-10-13 10:01 (:0)