请给出linux中查看系统已经登录用户的命令？

w命令

第一行：当前系统运行了多久和系统负载

谁正在远程登录系统并且在干什么

 [root@martin ~]# w
  11:30:33 up 4 days, 18:10,  2 users,  load average: 0.00, 0.00, 0.00
 USER     TTY      FROM              LOGIN@   IDLE   JCPU   PCPU WHAT
 root     pts/0    10.10.10.1   10:50    0.00s  0.03s  0.00s w
 root     pts/1    10.10.10.1   10:51   37:58   0.00s  0.00s -bash

who命令

显示谁正在远程登录和登录的详细时间

[root@martin ~]# who
root     pts/0        2017-04-10 10:50 (10.10.10.1)
root     pts/1        2017-04-10 10:51 (10.10.10.1)

last命令

显示最近远程登录的用户和查看已经登录的用户

 [root@martin ~]# last
 root     pts/1        10.10.10.1   Mon Apr 10 10:51   still logged in   #正在远程登录的用户
 root     pts/0        10.10.10.1   Mon Apr 10 10:50   still logged in
 root     pts/0        10.10.10.1   Fri Apr  7 14:54 - 18:49  (03:54)
 root     pts/0        10.10.10.1   Fri Apr  7 11:33 - 11:53  (00:20)
 root     pts/0        10.10.10.1   Fri Apr  7 11:28 - 11:31  (00:02)
 root     pts/0        10.10.10.1   Fri Apr  7 11:03 - 11:21  (00:17)
 root     pts/0        10.10.10.1   Thu Apr  6 10:58 - 14:42  (03:44)
 reboot   system boot  2.6.32-431.el6.x Wed Apr  5 17:20 - 11:37 (4+18:17)
 root     tty1                          Wed Apr  5 17:19 - down   (00:00)
 reboot   system boot  2.6.32-431.el6.x Wed Apr  5 17:18 - 17:20  (00:01)

lastlog命令

显示系统中所用用户的最近一次的登录信息

 [root@martin ~]# lastlog
 Username         Port     From             Latest
 root             pts/1    10.10.10.1       Mon Apr 10 10:51:42 +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**
 gopher                                     **Never logged in**
 ftp                                        **Never logged in**
 nobody                                     **Never logged in**
 vcsa                                       **Never logged in**
 saslauth                                   **Never logged in**
 postfix                                    **Never logged in**
 sshd                                       **Never logged in**
 centos                                     **Never logged in**

本文参考自 “李导的博客” 博客，原地址http://lidao.blog.51cto.com/3388056/1913667