Shell Primer-grep Filter-1

The regular expression is a string. There is a certain pattern. We use the specified string to match a specified line. The specified string is the regular expression.

Regular expressions have these tools: grep egrep sed awk

Command: Gerep

Description: Filters out the specified rows

Option:--color keywords have color

-N Display Line number

-C shows how many rows have appeared altogether

-V takes a row that does not contain the specified character

-a n n refers to a number, such as A2, which displays two lines below the line with the specified character

-B n n refers to a number such as B2 to display two lines above the line with the specified character

-c n n refers to numbers such as C2 the lines above and below the line with the specified characters.

-R Displays the rows in the directory with the specified characters

-RH display in the directory the line with the specified character does not display the file path and filename

grep filters out the rows with root

[[email protected] ~]# grep--color ' root '/etc/passwd
root: x:0:0:root:/root:/bin/bash
operator:x:11:0:operator:/root:/sbin/nologin

Grep-n

[[email protected] ~]# grep-n ' root '/etc/passwd
1:root:x:0:0:root:/root:/bin/bash
11:operator:x:11:0:operator:/root:/sbin/nologin

Create an individual name for grep and copy the/etc/passwd

[[email protected] ~]# vim. BASHRC

Alias cg= ' grep--color '

[Email protected] ~]# cp/etc/passwd 1.txt
CP: Do you want to overwrite "1.txt"? Y

-C

[[email protected] ~]# cg-c ' root ' 1.txt
2

-V

[[email protected] ~]# cg-v ' root ' 1.txt
Bin:x:1:1:bin:/bin:/sbin/nologin
Daemon:x:2:2:daemon:/sbin:/sbin/nologin
Adm:x:3:4:adm:/var/adm:/sbin/nologin
Lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
Sync:x:5:0:sync:/sbin:/bin/sync
Shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown

....

-A

[[email protected] ~]# cg-n-A 2 ' root ' 1.txt
1:root: x:0:0:root:/root:/bin/bash
2-bin:x:1:1:bin:/bin:/sbin/nologin
3-daemon:x:2:2:daemon:/sbin:/sbin/nologin
--
11:operator:x:11:0:operator:/root:/sbin/nologin
12-games:x:12:100:games:/usr/games:/sbin/nologin
13-gopher:x:13:30:gopher:/var/gopher:/sbin/nologin

-B

[[email protected] ~]# cg-n-b1 ' root ' 1.txt
1:root: x:0:0:root:/root:/bin/bash
--
10-uucp:x:10:14:uucp:/var/spool/uucp:/sbin/nologin
11:operator:x:11:0:operator:/root:/sbin/nologin

-C

[[email protected] ~]# cg-n-c1 ' root ' 1.txt
1:root: x:0:0:root:/root:/bin/bash

2-bin:x:1:1:bin:/bin:/sbin/nologin
--
10-uucp:x:10:14:uucp:/var/spool/uucp:/sbin/nologin
11:operator:x:11:0:operator:/root:/sbin/nologin
12-games:x:12:100:games:/usr/games:/sbin/nologin

-R

[[email protected] ~]# cg-r ' root ' ~

.....

/root/.bash_history:home=/root
/root/.bash_history:grep ' Root '/etc/passwd
/root/.bash_history:grep-n ' Root ' 1.txt
/root/.bash_history:grep-c ' Root ' 1.txt
/root/.bash_history:grep-v ' Root ' 1.txt
/root/.bash_history:grep-a2 ' Root ' 1.txt
/root/.bash_history:grep-n-a2 ' root ' 1.txt
/root/.bash_history:grep-n-b2 ' root ' 1.txt
/root/.bash_history:grep ' Root '/etc/passwd
/root/.bash_history:grep-n ' Root '/etc/passwd
/root/.bash_history:cg-c ' Root ' 1.txt

.......

[[email protected] ~]# cg-rh ' root ' ~

....

Home=/root
grep ' Root '/etc/passwd
Grep-n ' Root ' 1.txt
Grep-c ' Root ' 1.txt
Grep-v ' Root ' 1.txt
Grep-a2 ' Root ' 1.txt
Grep-n-a2 ' root ' 1.txt
Grep-n-b2 ' root ' 1.txt
grep ' Root '/etc/passwd
Grep-n ' Root '/etc/passwd
Cg-c ' Root ' 1.txt

......

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Summary: Vim ~/.BASHRC//alias cg= ' grep--color '

Cg-n-v-c-R-RH-AN-BN-CN

Shell Primer-grep Filter-1