Linux grep Regular Expression

Command alias Settings
An alias can be used when the command is very long
See what aliases are available
#alias
#alias rm= ' Rm-i '
Remove command aliases
#unalias LM

grep can parse a line of text, get the keyword, if the line exists in the keyword, will be the whole row out.

grep [-ACINV] [--color=auto] ' search string ' filename

-A: binary files are searched for data in the form of a text file
-C: Count the number of ' search strings ' found
-I: Ignores case differences, so case is considered the same
-N: Output line number
-V: Reverse selection, which shows the line without the ' search string ' content!

#grep-N root/etc/passwd

Find Jsen or JSON in the current directory
#grep-N Js[eo]n *

Regular expressions

[]: Match [] inside the character, it represents only a "one" character, can be a single character, or it can be a sequence of characters. can be used-to denote [] the range of character sequences, as in [1-5] instead of [12345]
^word: string to be searched (word) at the beginning of the line example: Grep-n ' ^# ' test.txt (find the row beginning with the beginning of #, parallel travel number)
word$: String to find word at line end
\: Escape character, special meaning of special symbol removal Example: grep-n \ ' test.txt find meaning single quote ' of the line
[^]: reverse Selection,
[^g]oo: Do not want OO front has g
. (decimal point): The representative must have an arbitrary character meaning
* (asterisk): represents the first character repeating 0 to an infinite number
\{n,m}\ successive N to M of the previous re character, if \{n}\ is a continuous n of the previous re character, if \{n\}\ is a continuous n more than the previous re character
Grep-n ' go\{2,3}\ ' g test.txt between G and G there are 2 to 3 o strings present

#grep-N [^g]oo test.txt

Oo don't want to have lowercase characters in front of you
#grep-N [^a-z]oo test.txt

Get the line with numbers
#grep-N [0-9] Test.text

The only one listed at the beginning of the line
#grep-n ' ^the ' test.txt
Don't want lowercase characters in front of OO
#grep-N [^a-z]oo test.txt

The line that starts with lowercase characters
#grep-N ^[a-z]oo test.txt
Or
#grep-n ' ^[[:lower:]] ' test.txt

Find the end of the line ending as a decimal point (.) Of that line
#grep-n ' \.$ ' test.txt
\ is an escape character

Blank line (command does not work)
#grep-n ' ^$ ' test.txt

No, it's the line.
Grep-v ' ^# '

Find out g?? The character of D, that is, a total of 4 characters
Grep-n ' G.. d ' test.txt

Find at least one O character before
Grep-n ' oo* ' test.txt

Both the beginning and the end are G, but there can be at least one o between the two G
Grep-n ' Goo*g ' test.test

Grep-n ' G*g '

The beginning of the end is G
Grep-n ' G.*g '

Any number line
Grep-n ' [0-9][0-9]* ' test.txt

Practice two O strings
Grep-n ' o\{2}\ '
{} has a special meaning in the shell, so it is necessary to use escape characters to lose special meaning characters

G after 2 to 5 O
Grep-n ' go\{2,5}\ ' test.txt

List connection file header will be ' lrwxrwxrwx '
#ls-L/etc | grep ' ^| '

Sed awk tool

SED can share standard input and can replace, delete, add, and select specific lines of data

#nl/etc/passwd | Sed ' 2,5d '
Delete Rows 2 to 5

Linux grep Regular Expression