linux 用户和组命令整理及详细介绍

1、列出当前系统上所有已经登录的用户名，注意：同一个用户登录多次，则只显示一次即可。

[root@node2 ~]# who 
root   pts/0    2016-10-08 13:28 (10.106.64.41)
root   pts/1    2016-10-08 13:44 (10.106.64.41)
root   pts/2    2016-10-08 14:22 (10.106.65.82)
root   pts/3    2016-10-08 14:22 (10.106.65.82)
root   pts/4    2016-10-08 15:26 (10.106.64.41)
root   pts/5    2016-10-08 15:26 (10.106.64.41)
root   pts/6    2016-10-08 15:26 (10.106.64.41)
[root@node2 ~]# who -m
root   pts/4    2016-10-08 15:26 (10.106.64.41)