who命令与w命令相似，但要比w命令显示更加详细的信息。
[root@rusky opt]# man who
WHO(1) User Commands WHO(1)

NAME
who - show who is logged on

SYNOPSIS
who [OPTION]... [ FILE | ARG1 ARG2 ]

DESCRIPTION
Print information about users who are currently logged in.

-a, --all
same as -b -d --login -p -r -t -T -u

-b, --boot
time of last system boot

-d, --dead
print dead processes

-H, --heading
print line of column headings

-l, --login
print system login processes

--lookup
attempt to canonicalize hostnames via DNS

-m only hostname and user associated with stdin

-p, --process
print active processes spawned by init

-q, --count
all login names and number of users logged on

-r, --runlevel
print current runlevel

-s, --short
print only name, line, and time (default)

-t, --time
print last system clock change

-T, -w, --mesg
add user‘s message status as +, - or ?

-u, --users
list users logged in

--message
same as -T

--writable
same as -T

--help display this help and exit

--version
output version information and exit
============
常用who命令：

[root@rusky opt]# who root pts/0 Dec 31 14:13 (192.168.1.111)rusky1 pts/1 Dec 31 15:58 (192.168.1.111)rusky1 pts/2 Dec 31 16:00 (192.168.1.111)[root@rusky opt]# who -b               --time of last system bootsystem boot Dec 27 05:06[root@rusky opt]# who -r               ---print current runlevelrun-level 5 Dec 27 05:06[root@rusky opt]# who -q               ---all login names and number of users logged onroot rusky1 rusky1# users=3[root@rusky opt]# who -sroot pts/0 Dec 31 14:13 (192.168.1.111)rusky1 pts/1 Dec 31 15:58 (192.168.1.111)rusky1 pts/2 Dec 31 16:00 (192.168.1.111)[root@rusky opt]# who -asystem boot Dec 27 05:06run-level 5 Dec 27 05:06LOGIN tty3 Dec 27 05:06 3508 id=3LOGIN tty2 Dec 27 05:06 3506 id=2LOGIN tty4 Dec 27 05:06 3510 id=4LOGIN tty5 Dec 27 05:06 3514 id=5LOGIN tty6 Dec 27 05:06 3516 id=6root + pts/0 Dec 31 14:13 . 31733 (192.168.1.111)rusky1 + pts/1 Dec 31 15:58 00:33 581 (192.168.1.111)rusky1 + pts/2 Dec 31 16:00 00:39 581 (192.168.1.111)pts/3 Dec 31 16:21 1084 id=ts/3 term=0 exit=0

linux查看用户登录信息2-who命令