Regular Expression 2--grep command

GREP is the abbreviation for global search Regular Expression and Print out of the line.

1. Basic usage of GREP commands

Command format: grep [options] [mode] [file ...]

Options	Significance
-C	Output only the number of matching rows
-I.	Ignore case when searching
-H	Do not display file names when querying multiple files
-L	Lists only matching file names, not specific matching rows
-N	List all matching rows and display line numbers
-S	Do not display error messages that do not exist or have no matching text
-V	Display all lines that do not contain matching text
-W	Match Whole word
-R	Recursive search not only searches the current working directory, but also searches subdirectories
-E	Support for extended regular expressions
-F	Regular expressions are not supported and are matched by the literal meaning of the string

Note: you need to enclose the pattern in double quotes as long as the pattern contains spaces.

grep Multi-file operation (AA BB for two files)

2. The meaning and usage of grep options 2.1-c options

In Aa,bb two files, there are two lines containing the Hello

2.2-n Options

The 1th line in the Aa,bb file contains Hello and prints out the information

2.3-v Options

2.4-i Options

Search in AA files for case-insensitive Hello all lines

2.5-l Options

Search all files in the current directory containing the text lines of Hello, listing only the file names

2.6-s Options

2.7-r Options

2.8-w and-X options

When the-w option is added, * is interpreted as a normal character.

-X means matching an entire row, which results when the file has an entire line of content to match.

2.9-q Options

Plus the-q option no longer outputs the result, but the exit status indicates success.

Exit Status 0 Indicates a successful search, exit status 1 indicates that a line of text that satisfies the pattern is not searched, and exit status 2 indicates that the command or program was not executed due to an error.

3 grep and regular expressions

3.1 Matching the beginning of the line

3.2 Set case

-I can ignore the case, or you can use [] to implement

3.3 Match repeating characters

Show h starts, repeats h any time, and the letter is E

3.4 Escape Character

Escape character \ Mask its meaning

Regular Expression 2--grep command