Regular and extended expressions, sed text processor and awk tool, changing IP address with script

1、 Regular expressions （grep）

        effect ：
Use a single string to describe it
Matches a series of strings that conform to a syntax rule  

       form ：
Ordinary characters and metacharacters   

       Metacharacters ：
[ ]  ： Any character in the middle bracket
[^] ： Except for any character in the middle bracket
^   ： Find the beginning of a line , What does it start with
$   ： Find end of line , What does it end with
.    ： Find any character
*   ： Look for duplicate characters
{ }  ： Find range of consecutive characters

        （1） Find specific characters -n Indicates display line number ,-i Indicates case insensitive ,-v Indicates reverse selection

grep -n 'the' test.txt

grep -in 'the' test.txt 

        （2） Using brackets “[ ]” To find set characters

Find a match “i” perhaps “o” The characters of

 grep -n 'sh[io]rt' test.txt

  lookup “oo” The front is not “w” String

grep -n '[^w]oo' test.txt

  lookup “oo” Lines with lowercase letters are not allowed in front

grep -n '[^a-z]oo' test.txt

Find rows that contain numbers

grep -n '[0-9]' test.txt

        （3） Find the beginning of a line “^” And end of line characters “$”

Find lines that start with lowercase letters

grep -n '^[a-z]' test.txt

  Find lines that do not start with letters

grep -n '^[^a-zA-Z]' test.txt

Looking to “.” The line at the end

grep -n '\.$' test.txt

        （4） Find any character “.” And repeating characters “*”
“.” Represents any character

grep -n 'w..d' test.txt

  The query contains at least two o The characters above

grep -n 'ooo*' test.txt

Query to w start d ending , At least one in between o String

grep -n 'woo*d' test.txt

Query to w start d ending , The middle character can have a string of optional characters

grep -n 'w.*d' test.txt

  Find the line of any number

grep -n '[0-9][0-9]*' test.txt

        （5） Find range of consecutive characters “{ }”

Check two o The characters of

grep -n 'o\{2\}' test.txt

Query to w start d ending , The middle contains 2-5 individual o String

grep -n 'wo\{2,5\}d' test.txt

Query to w start d ending , The middle contains 2 More than o String

grep -n 'wo\{2,\}d' test.txt

 2、 Extended regular expression （egrep）

Duplicate query o

egrep -n 'wo+d' test.txt

Inquire about ”tast" perhaps "test" character string

egrep -n 't(a|e)st' test.txt

  The blank line and the beginning of the line in the query file are “#” Outside the line

egrep  -v   '^$|^#'  test.txt

3、Sed File processor

 -e： Represents a text file that uses a specified command or script to process input
 -f： Indicates that the input text file is processed with the specified script file
 -n： Show only processed results
-i： Edit text file directly

a： increase , Add a line below the current line to specify
c： Replace , Replace the selected row with the specified content
d： Delete . Delete selected rows
i： Insert . Insert a row above the selected row to specify

        （1） Output eligible text p Indicates normal output

Output everything

 sed -n 'p' test.txt

  Output No 3 That's ok

sed -n '3p' test.txt

  Output all odd rows ,n Read in the next line

sed -n 'p;n' test.txt

Output No 1-5 Odd rows between rows

sed -n  '1,5{p;n}' test.txt

  Output No 10 Even lines from line to end of file

sed -n '10,${n;p}' test.txt

The output contains the The line of  

sed -n '/the/p' test.txt

Output to PI Beginning line  

sed -n '/PI/p' test.txt

  Output lines ending in numbers

sed -n '/[0-9]$/p' test.txt

  Output contains words wood The line of

sed -n '/\<wood\>/p' test.txt

        （2） Delete eligible text （d）

Delete the first 3 That's ok

nl test.txt  | sed '3d'

Delete the first 3-5 That's ok

nl test.txt | sed '3,5d'

  Delete include cross The line of

 nl test.txt  | sed '/cross/d'

Delete lines that start with lowercase letters

sed '/^[a-z]/d' test.txt

Delete with “.” The line at the end

sed '/\.$/d' test.txt

Delete all blank lines

sed '/^$/d' test.txt

        （3） Replace eligible text

First in each line the Replace with THE

sed  's/the/THE/'   test.txt 

Put all in each line the Replace with THE

sed  's/the/THE/g'  test.txt 

Insert at the beginning of each line # Number

sed   's/^/#/'    test.txt

Insert a string at the end of each line EOF

sed  's/$/EOF/'    test.txt 

Will include the Of all rows o Replace with O

sed  '/the/s/o/O/g'  test.txt

         (4) Migrate eligible text
 

In the 3 Insert a new row after row , The content is New

sed  '3aNew'   test.txt  

Include in the Insert a new row after each row of , The content is New

sed  '/the/aNew'  test.txt 

In the 3 Insert multiline content after row , In the middle of the \n Means line break

sed  '3aNew1\nNew2'   test.txt

        (5)sed Direct operation of documents

Write a script , Close the firewall and selinux, And configuration IP by 192.168.1.10

vim ip.sh
#!/bin/bash
systemctl stop firewalld
systemctl disable firewalld
setenforce 0
sed -i '/dhcp/d' /etc/sysconfig/network-scripts/ifcfg-ens33
sed -i '/UUID/d' /etc/sysconfig/network-scripts/ifcfg-ens33
sed -i '$aIPADDR=192.168.1.10' /etc/sysconfig/network-scripts/ifcfg-ens33
systemctl restart network


chmod +x ip.sh

./ip.sh

Used to adjust vsftpd Service configuration ： No anonymous users , But allow local users to （ It is also allowed to write ）
 

#!/bin/bash
SAMPLE="/usr/share/doc/vsftpd-3.0.2/EXAMPLE/INTERNET_SITE/vsftpd.conf"
CONFIG="/etc/vsftpd/vsftpd.conf"
[ ! -e  "$CONFIG.bak" ] && cp $CONFIG $CONFIG.bak
sed -e  '/^anonymous_enable/s/YSE/NO/g' $SAMPLE > $CONFIG
sed -i -e   '/^local_enable/s/NO/YES/g' -e  '/^write_enable/s/NO/YES/g' $CONFIG
grep "listen" $CONFIG || sed -i '$alisten=YES' $CONFIG
sed -i '$apam_service_name=vsftpd' $CONFIG
sed -i '/^one/s/^/#' $CONFIG
systemctl restart vsftpd
systemctl enable vsftpd

 4、awk Tools

        （1） Output text by line

Output No 1~3 Row content

awk   'NR==1,NR==3{print}'   test.txt

Output No 1 That's ok , The first 3 Row content

awk   'NR==1||NR==3{print}'   test.txt

    // Output to root Beginning line

awk   '/^root/{print}'  /etc/passwd

        （2） Output text by field

Output in each line （ Space off ） Of the 1,3 A field

awk  '{print $1,$3}'  test.txt