How to deal with Linux regular expressions

How to fix Linux regular expressions, for this problem, this article details the corresponding analysis and solution, hoping to help more small partners who want to solve this problem find a simpler and easier way.

A regular expression is a pattern of characters used to match specified characters during a lookup.

Metacharacters are generally divided into two categories in Linux:

Shell metacharacters, parsed by Linux Shell;

Regular expression metacharacters, parsed by text processing tools such as vi/grep/sed/awk;

Regular expressions are typically processed as lines of text. Set the--color parameter for the grep command before doing the following example:

Each time the string is filtered out, it will be colored.

One more thing you need to do before you start is create a re-file for testing, which reads as follows:

Document content extracted from

regular expression metacharacters

special metacharacters

Extended regular expressions

practical operation

Matches all rows that begin with love

Match all lines at the end of love

Matches all lines that start with l, contain two characters in the middle, and end with e

Matches 0 or more blank lines followed by love characters

Match Love or Love

Match letters A-Z, followed by ove

Matches any character line that is not in the A-Z range, all lowercase characters

Love.

matching space

Match any character

Repeat the preceding o character 2 to 4 times

Repeat the o character at least 2 times

Repeat 0 character up to 2 times

Repeat the previous character one by one or one by

0 or one character

or, find multiple strings

Group filtering matching

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