Common parameters and usage of grep command

1, grep introduction
The grep command is a powerful text search tool in a Linux system that uses regular expressions to search for text and print matching rows. grep full name Global Regular Expr ession Print, which represents the global regular expression version, with permissions that are available to all users. grep is available for shell scripts because grep indicates the state of the search by returning a status value, returns 0 if the template search succeeds, or 1 if the search is unsuccessful, and returns 2 if the searched file does not exist.
2, grep commonly used parameters
-A: binary files are searched for data in the form of text files
-C: Calculates the number of ' match strings ' found
-I: Ignores case differences, so capitalization is considered the same
-N: By the way output line number
-V: Reverse selection, which shows the line with no ' search string ' content.
For example, the Test.txt file reads as follows:

1000 nan
1001 NV 1002-
Nan

Ignore case to match and display line number

Grep-ni ' nan ' test.txt

1:1000 nan
3:1002

Ignore case for "non" match and display line number

Grep-ni ' nan ' test.txt

2:1001 NV

3, grep regular expression

Re	Meaning
^word	The string to match (word) is at the beginning of the line. such as: grep ' ^1000 ' test.txt return: 1000 Nan
word$	The string to match (word) at the end of the line. such as: grep ' nv$ ' test.txt Return: 1001 NV
.	Represents any one character, it must be any character. The searched string can be (Eve) (Eae) (EEE) (e e), but not just (EE). There must be only one character between E and E, and spaces is also a character. such as: grep ' N.N ' test.txt return: 1000 Nan
\	Escape character, special character Furu ' {} such as: grep-n \ ' Test.txt Match the line that contains single quotes.
*	Repeat 0 or more of the previous re characters, note that there must be characters in front of the * number such as: grep ' n ' test.txt return: 1000 Nan 1001 NV 1002 Nan
\{n,m\}	The last re character of continuous N to M If the \{n\} is a continuous n of the previous re character, If \{n,\} is a continuous n more than the previous re characters.
[ ]	Character set combination of RE special character symbol [ABC]: means to match A or B or C [A-Z]: Represents a match a,b,c,... Z any of these 26 letters [^a-z]: Indicates that the beginning of a string can match a successful one, as long as it is not the lowercase letter A-Z [a-z$]: Indicates that the end of a string can match a successful one if it is a lowercase letter A-Z

Extended Regular expression: egrep ' pattern ' file.txt or with Grep-e ' file.txt

Re	Meaning
+	Repeat "one or more" of the previous re characters such as: Egrep-n ' go+d ' regular_express.txt Then: (God) (good) (Goood) etc will match successfully
?	The first re character of "0 or one" such as: Egrep-n ' go?d ' regular_express.txt Then: (GD) (God) etc will match successfully
|	Find a number of strings in or (or) such as: Egrep-n ' Gd|good ' regular_express.txt Then: match the GD or good these two strings
()	Find the "group" string such as: Egrep-n ' G (la|oo) d ' regular_express.txt Then: Match (Glad) or (good) these two strings