Several commands of W

several commands of W

WhoAmI View current logged on user

W.H.O.

[[email protected] ~]# who shows which users are currently logged on to the system

User name     Login Terminal Logon Hours

Root Tty1 2016-06-06 17:57

Root pts/0 2016-06-06 18:01 (192.168.50.1)

Terminal type:

Pty: Physical terminal.

Console: Control console. (VGA card)

TTY: virtual terminal (VGA card)

TTYs: serial terminal

pts/#: Pseudo terminal

Who–r Display the current run level

Who–h Display Head

[Email protected] ~]# Who-r

Run Level 3 2016-06-06 17:39

[Email protected] ~]# who-h

name       Line           Time Notes

Root Tty1 2016-06-06 17:57

Root pts/0 2016-06-06 18:01 (192.168.50.1)

View admin user has no login

[[email protected] ~]# who |grep admin

[[email protected] ~]# who |grep admin

[[email protected] ~]# echo $?

1

write a script. See If the admin user is logged in every 5 seconds. If you sign in, you are logged in, and you exit the script.

Sleep # delay for a few seconds

#!/bin/bash

#

For I in {1..100000000};d o

Sleep 5

Who |grep admin &>/dev/null

If [$?-eq 0];then

echo "Admin Denglu"

Exit 0

Fi

Done

W

[[Email protected]~]# w is similar to WHO, command more detailed than who

19:24:56 up 1:45, 3 users, Load average:0.00, 0.00, 0.00

USER TTY from [email protected] IDLE jcpu PCPU

Root tty1-17:57 1:25m 0.05s 0.05s-bash

Root pts/0 192.168.50.1 18:01 0.00s 0.24s 0.00s W

Admin pts/1 192.168.50.1 19:21 3:10 0.01s 0.01s–bash

                                                                                                                                                                               &nbsP

Last show logged in information

[[email protected] ~]# last display /var/log/wtmp file, showing the user's login history and system restart history

Admin PTS/1 192.168.50.1 Mon June 6 19:21 still logged in

Admin PTS/1 192.168.50.1 Mon June 6 19:19-19:21 (00:01)

Root pts/0 192.168.50.1 Mon June 6 18:01 still logged in

Root Tty1 Monjun 6 17:57 still logged in

Reboot system boot 2.6.32-504.el6.i monjun 6 17:39-19:27 (01:47)

Last–n 3 shows only the last three times

Lastb display /var/log/btmp file , user Error login attempt

[Email protected] ~]# LASTB

Chenlon tty1 Mon June 6 17:57-17:57 (00:00)

Btmp begins Mon June 6 17:57:27 2016

Last–n 3 shows only the last three times

Lastlog Displays the most recent successful login information for each user of the current system

-uusername: Displays the most recent login information for the specified user

[Email protected] ~]# lastlog-u root

User name     Port             from Last Login Time

Root pts/0 192.168.50.1 6 months 6 18:01:31 +0800 2016

basename Get the file name under the path

[Email protected] ~]# BASENAME/ETC/PASSWD

passwd

BaseName $ Show the name of the script itself

$ A script path and name when executing a script

Mail messages. The message is stored in the Mbox directory in the user's home directory

D means delete message

R means reply message

-S message subject

[Email protected] ~]$ cat/etc/passwd |mail–s "How is it?" Root sends the cat 's message to root as the email content

[[Email protected] ~]# mail

Heirloom Mail Version 12.4 7/29/08. Type? For help.

"/var/spool/mail/root": 2messages 2 new

>n 1 [email protected] Monjun 6 19:49 48/2099

N [email protected] Mon June 6 19:49 47/2014 "How is it?"

Enter numbers directly See mail

Hostname Display the host name of the current host can also change the real-time hostname, $HOSTNAME

Write a script if the current hostname is not Zhongguo, change to Zhongguo

if the current hostname is localhost , change to Zhongguo

#!/bin/bash

#

[' hostname '! = Zhongguo]&&hostname Zhongguo

[' hostname ' = localhost]&&hostname Zhongguo
if the current host name is empty, or if the (none) , or you can change it to Zhongguo for localhost

[[Email protected] ~]# [-Z ' hostname '] | | [' hostname ' = = ' (none) '] | | [' hostname ' = = ' localhost '] && Hostnamezhongguo

Generate random numbers

random:0-32768

Random number generator:

/dev/random

/dev/urandom

generate a random number and get the maximum value from it

#!/bin/bash

#

For I in {1..10};d o

echo $RANDOM >>/tmp/sort.txt

Done

Cat/tmp/sort.txt | Sort-n |TAIL-1

Or take the maximum number and the minimum number

#!/bin/bash

#

Declare-i max=0

Declare-i min=0

For I in {1..10};d o

g= $RANDOM

[$I-eq 1] && min= $G

if[$I-le 9];then

Echo-n "$G,"

Else

echo "$G"

Fi

[$G-gt $MAX] && max= $G

[$G-lt $MIN] && min= $G

Done

echo "$MAX, $MIN"

This article from "Linux operation and Maintenance" blog, declined reprint!

Several commands of W