文章转载而来，但是每个命令都需要测试！
方法1-linux里面最短的命令---w
w命令的解释是-显示谁远程登录了系统并且在干什么
[root@show regular]# w
20:01:54 up 6 days, 46 min, 5 users, load average: 0.00, 0.00, 0.00
USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT
root pts/0 10.0.0.1 08:23 0.00s 0.43s 0.00s w
root pts/1 10.0.0.1 20:01 5.00s 0.00s 0.00s -bash
w不只能看用户的登录状态，还能看他们在执行什么命令。
同时还可以看当前系统运行了多久和系统负载----第一行就行 这个相当于uptime命令。
who---显示谁远程登录了
[root@show ~]# who
root pts/0 2017-04-07 08:23 (10.0.0.1)
root pts/1 2017-04-07 20:01 (10.0.0.1)
last--显示最近远程登录的用户-也可以查看已经登录的用户
[root@show ~]# last |head -20
root pts/5 10.0.0.1 Fri Apr 7 21:10 still logged in
root pts/4 10.0.0.1 Fri Apr 7 20:01 still logged in
root pts/3 10.0.0.1 Fri Apr 7 20:01 still logged in
root pts/2 10.0.0.1 Fri Apr 7 20:01 still logged in
root pts/1 10.0.0.1 Fri Apr 7 20:01 still logged in
root pts/0 10.0.0.1 Fri Apr 7 08:23 still logged in
root pts/0 10.0.0.1 Thu Apr 6 08:25 - 22:16 (13:50)
root pts/1 10.0.0.1 Wed Apr 5 20:26 - 10:16 (13:50)
root pts/0 10.0.0.1 Tue Apr 4 23:12 - 21:52 (22:39)
root pts/1 10.0.0.1 Fri Mar 31 20:36 - 09:46 (13:09)
root pts/0 10.0.0.1 Fri Mar 31 15:47 - 21:55 (06:08)
上面显示的still logged in 就表示，现在正在远程登录的用户
lastlog-显示系统中所用用户的最近一次的登录信息
[root@show ~]# lastlog
Username Port From Latest
root pts/5 10.0.0.1 Fri Apr 7 21:10:15 +0800 2017
bin **Never logged in**
daemon **Never logged in**
adm **Never logged in**
lp **Never logged in**
sync **Never logged in**
shutdown **Never logged in**
halt **Never logged in**
mail **Never logged in**
uucp **Never logged in**
operator **Never logged in**
games **Never logged in**
