How to use regular expressions in Linux system

Regular expressions are not unique to Linux systems, but regular expressions are a widely used representation in Linux systems. This article will give a brief introduction to the use of regular expressions in Linux systems.

I. Regular Expressions

In computer science, regular expressions are used to describe or match a series of strings that conform to a syntactic rule; in a text editor or some tool In a bash environment, for example, regular expressions are often used to retrieve textual content that conforms to a pattern. In Linux, regular expressions are patterns written by a type of character. Filtering the required strings in the bash environment by implementing a defined pattern.

A regular expression consists of a series of ordinary characters and some metacharacters. Ordinary characters mainly include uppercase and lowercase letters and numbers. Metacharacters have a special meaning. It does not represent the meaning of the characters themselves but is used for additional functional descriptions. Regular expressions have basic regular expressions and extended regular expressions. Below I will list some commonly used metacharacters commonly used in Linux, and use related examples to explain:

1. Basic regularization Expressions

2. Extending regular expressions

The following mainly lists some metacharacters that differ from basic regular expressions.

3. There are other things in Linux. Escape characters, but here are just a few listings and explanations for commonly used ones. Interested friends can view the help system provided in the man documentation through “man 7 regex”.

Second, the use of grep command

Let me introduce how to use the grep command to use the regular expression for the corresponding pattern matching. First let me introduce the basic use of the grep command.

grep (Global Search Regular Expression and Printing), which means comprehensive search for regular expressions and printing. It is a powerful text search tool that can search for text using regular expressions and print matching lines. come out. There are three types of grep, including grep, egrep, and fgrep.

Respectively:

The above is the use of regular expressions in Linux. Of course, the introduction of this article is general, but basically covers all the uses of regular expressions in Linux. .