NAME
users - print the user names of users currently logged in to the current host
SYNOPSIS
users [OPTION]... [FILE]
DESCRIPTION
Output who is currently logged in according to FILE. If FILE is not specified, use /var/run/utmp. /var/log/wtmp as FILE is common.
users命令用单独的一行打印出当前登录的用户，每个显示的用户名对应一个登录会话。如果一个用户有不止一个登录会话，那他的用户名将显示相同的次数。
原文：http://www.cnblogs.com/itcomputer/p/4644433.html