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/ Dec : (192.168.1.111)
rusky1 pts/ Dec : (192.168.1.111)
rusky1 pts/ Dec : (192.168.1.111) [root@rusky opt]# who -b --time of last system boot
system boot Dec : [root@rusky opt]# who -r ---print current runlevel
run-level Dec : [root@rusky opt]# who -q ---all login names and number of users logged on
root rusky1 rusky1
# users= [root@rusky opt]# who -s
root pts/ Dec : (192.168.1.111)
rusky1 pts/ Dec : (192.168.1.111)
rusky1 pts/ Dec : (192.168.1.111) [root@rusky opt]# who -a
system boot Dec :
run-level Dec :
LOGIN tty3 Dec : id=
LOGIN tty2 Dec : id=
LOGIN tty4 Dec : id=
LOGIN tty5 Dec : id=
LOGIN tty6 Dec : id=
root + pts/ Dec : . (192.168.1.111)
rusky1 + pts/ Dec : : (192.168.1.111)
rusky1 + pts/ Dec : : (192.168.1.111)
pts/ Dec : id=ts/ term= exit=