(6) VIM editor MV cat redirection standard input and output more pipe symbols head tail

One 、 Knowledge supplement

1.1 env

Check the current terminal shell Of environment variable （ Global variables ）

Among the contents found HISTSIZT=1000, That is, the number of historical orders is 1000

1.2 vim Use of editor

Linux Text editor under ,vi Updated version of

【 install vim Editor 】yum install vim -y（ The virtual machine must be able to access the Internet ）

1.2.1 touch and vim The difference between creating files

touch a.txt Just create an empty file , Don't write content into the file

vim a.txt Not only create files , At the same time, you can write content into it . If a.txt The file already exists , Is the use of vim Open this file , If it does not exist, it is new

1.2.2 Operation steps

1. Press i Enter input （ Insert ） Pattern
2. Press Esc Key to return to command mode
3. Input :wq（ Must be in English input mode , A lowercase letter ）==> Exit and save
4. It can be done by cat Connect the file name to check the file content

[[email protected] lianxi]# vim lihua.txt
[[email protected] lianxi]# cat lihua.txt
lihua
Chian
hunan
 Li Hua 
 China 

Two 、 Command to explain

        2.1 mv

1. Move （Move） File or directory ==> shear

[[email protected] lianxi]# ls
hua.txt  hunan  lihua
[[email protected] lianxi]# mv lihua hunan
[[email protected] lianxi]# ls
hua.txt  hunan
[[email protected] lianxi]# ls hunan
lihua

You can move multiple folders at the same time , You can also move files and folders at the same time . here , The destination must be a folder , Otherwise, it cannot accommodate multiple contents

[[email protected] lianxi]# mkdir liming
[[email protected] lianxi]# touch lihua.txt
[[email protected] lianxi]# ls
hua.txt  hunan  lihua.txt  liming
[[email protected] lianxi]# mv lihua.txt  liming/ hunan
[[email protected] lianxi]# ls
hua.txt  hunan
[[email protected] lianxi]# ls hunan
lihua  lihua.txt  liming

2. If the target location is the same as the original location or the target folder does not exist , Is quite renamed ==> rename

[[email protected] lianxi]# ls
hua.txt  hunan
[[email protected] lianxi]# mv hunan xiang
[[email protected] lianxi]# ls
hua.txt  xiang

        2.2 cat

Show the full contents of the file

【 Options 】-n Number each line of output

[[email protected] lianxi]# file lihua.txt
lihua.txt: UTF-8 Unicode text
[[email protected] lianxi]# cat -n lihua.txt
     1  lihua
     2  Chian
     3  hunan
     4   Li Hua 
     5   China 

        2.2.1 cat Detailed functions

cat - concatenate files and print on the standard output

         Connect files and output content to the screen

Connection file ： At the same time, the contents of multiple files can be output at the same time , And connect them

[[email protected] lianxi]# cat lihua.txt
lihua
Chian
hunan
 Li Hua 
 China 
[[email protected] lianxi]# cat xiaoming.txt
Hello
xiaoming
[[email protected] lianxi]# cat lihua.txt  xiaoming.txt
lihua
Chian
hunan
 Li Hua 
 China 
Hello
xiaoming

        2.2.2 Redirect

Put the content that should be output on the screen , Redirect to a file , Changed his output direction

standard input Standard input ==》 keyboard

standard output Standard output ==》 The screen

Redirection actually changes the direction of output , The standard output is to output to the screen , Redirection can be output to a file

[[email protected] lianxi]# cat lihua.txt  xiaoming.txt >lihua_xiaoming.txt
[[email protected] lianxi]# ls
hua.txt  lihua.txt  lihua_xiaoming.txt  passwd  xiang  xiaoming.txt
[[email protected] lianxi]# cat lihua_xiaoming.txt
lihua
Chian
hunan
 Li Hua 
 China 
Hello
xiaoming

> Output redirection ： If the following file does not exist, create , If it exists, the original content will be overwritten

[[email protected] lianxi]# echo hello,world >hello.txt
[[email protected] lianxi]# ls
hello.txt  hua.txt  lihua.txt  lihua_xiaoming.txt  passwd  xiang  xiaoming.txt
[[email protected] lianxi]# cat hello.txt
hello,world
[[email protected] lianxi]# echo HELLO,WORLD >hello.txt
[[email protected] lianxi]# cat hello.txt
HELLO,WORLD

>> Append output redirection ： If the following file does not exist, create a new , If it exists, the original content will not be overwritten , Just append at the end

[[email protected] lianxi]# echo 123 >test.txt
[[email protected] lianxi]# cat test.txt
123
[[email protected] lianxi]# echo 456 >>test.txt
[[email protected] lianxi]# cat test.txt
123
456

        2.2.3 tac

Read the contents of the file upside down

[[email protected] lianxi]# cat test.txt
123
456
[[email protected] lianxi]# tac test.txt
456
123

        2.3 more

Full screen display of file content

Pagination display ： Page by page display

        2.3.1 Interactive operation method

1. Press Enter Key down line by line
2. Press the space bar to scroll down one screen , Press b Key up one screen
3. Press q Key to exit

[[email protected] lianxi]# cp /var/log/messages .
[[email protected] lianxi]# more messages

        2.3.2 | Pipe symbol

The function is to send the output of the previous command to the following command as input

Pipeline essentially realizes the communication between processes , It is a way of communication between processes

[[email protected] lianxi]# cat -n messages |more     The line number is displayed , There is paging display 

        2.3.3 ps aux

see Linux Information about the current instantaneous process in the system

• USER Refers to which user started the process
• PID Is the number of the process process id
• %CPU Consumed by the process cpu Usage rate
• %MEM Memory consumed by the process memory
• COMMAND Is the name of the running process

[[email protected] lianxi]# ps aux
USER        PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root          1  0.0  0.6 128148  6756 ?        Ss   2 month 14   0:05 /usr/lib/syst
root          2  0.0  0.0      0     0 ?        S    2 month 14   0:00 [kthreadd]
root          4  0.0  0.0      0     0 ?        S<   2 month 14   0:00 [kworker/0:0H

        2.3.4 wc

Count the number of lines in a file 、 word 、 byte

• first 2 Express 2 That's ok
• the second 2 Express 2 Word
• 8 Represents eight bytes

A Chinese character occupies 3 Bytes , An English letter accounts for 1 Bytes , A space 、 A enter key takes up one byte

[[email protected] lianxi]# cat test.txt
123
456
[[email protected] lianxi]# wc test.txt
2 2 8 test.txt
[[email protected] lianxi]# cat test.txt |wc -l    Statistics test.txt How many lines are there in the document 
2

ps aux|wc -l Statistics ps aux How many lines of command output

ps aux|more Display process information in pages

        【 Options 】

-l The statistical number of rows

-w Count the number of words

-c Count bytes

        2.3.5 $()

effect ： Give priority to the commands inside , Then return the execution result of the command

user_num=$(cat /etc/passwd |wc -l) Execute first cat /etc/passwd |wc -l Get the results , And then assign it to user_num This variable

[[email protected] lianxi]# cat /etc/passwd |wc -l
30
[[email protected] lianxi]# user_num=$(cat /etc/passwd |wc -l)
[[email protected] lianxi]# echo $user_num
30

        2.3.6 less

And more The same command , But there are more extensions , The operation method is basically similar , There are some differences

【page down】 Page up 【page up】 Page down

        【 differences 】more and less

1. After the content is displayed ,less Do not exit ,more Will automatically exit
2. less Can press 【page down】【page up】, and more no way

        2.4 head

purpose ： Look at the beginning of the file （ Default is header 10 That's ok ）

Format ：head -n numbuer file name

Format ：head - Numbers file name

[[email protected] lianxi]# head -3 messages be equal to [[email protected] lianxi]# head -n 3 messages

[[email protected] lianxi]# cat -n messages |head -3
     1  Feb 13 17:27:01 192 rsyslogd: [origin software="rsyslogd" swVersion="8.24.0-55.el7" x-pid="1069" x-info="http://www.rsyslog.com"] rsyslogd was HUPed
     2  Feb 13 17:37:33 192 dhclient[864]: DHCPREQUEST on ens33 to 192.168.255.254 port 67 (xid=0x7c8e74b0)
     3  Feb 13 17:37:33 192 dhclient[864]: DHCPACK from 192.168.255.254 (xid=0x7c8e74b0)

        2.5 tail

purpose ： Look at the end of the file （ The default is after 10 That's ok ）

Format ：tail -n numbuer file name

Format ：tail - Numbers file name

        2.5.1 tail Advanced usage of

tail -n +number Used before you don't want to display number The content of the line , Show from page number From the beginning to the end of the line

[[email protected] lianxi]# df -Th
 file system                  type        Capacity    Already used    You can use   Already used %  Mount point 
devtmpfs                devtmpfs  475M     0  475M    0% /dev
tmpfs                   tmpfs     487M     0  487M    0% /dev/shm
tmpfs                   tmpfs     487M  7.7M  479M    2% /run
tmpfs                   tmpfs     487M     0  487M    0% /sys/fs/cgroup
/dev/mapper/centos-root xfs        17G  1.6G   16G   10% /
/dev/sda1               xfs      1014M  138M  877M   14% /boot
tmpfs                   tmpfs      98M     0   98M    0% /run/user/0
[[email protected] lianxi]# df -Th|tail -n +2    From the second line to the end 
devtmpfs                devtmpfs  475M     0  475M    0% /dev
tmpfs                   tmpfs     487M     0  487M    0% /dev/shm
tmpfs                   tmpfs     487M  7.7M  479M    2% /run
tmpfs                   tmpfs     487M     0  487M    0% /sys/fs/cgroup
/dev/mapper/centos-root xfs        17G  1.6G   16G   10% /
/dev/sda1               xfs      1014M  138M  877M   14% /boot
tmpfs                   tmpfs      98M     0   98M    0% /run/user/0

tail -f test.txt Dynamic monitoring test.txt Changes in the contents of the document ： Stare at the end of the file , Once there is input , Output to the user immediately

It is generally used when we look at the change of a log file

Press Ctrl + C force finish

[[email protected] lianxi]# tail -f test.txt
123
456
HELLO
TEST

（ Copy label ） Use the redirection function in another terminal to add

[[email protected] ~]# cd lianxi
[[email protected] lianxi]# echo HELLO >>test.txt
[[email protected] lianxi]# echo TEST >>test.txt