Regular expression (Regular Expression) is a text pattern that includes ordinary characters (for example, letters between a to z) and special characters (called "metacharacters").
Regular expressions use a single string to describe and match a series of strings that match a syntactic rule.
Regular expressions are tedious, but it is powerful. The application after learning will let you not only increase efficiency, but also bring you a sense of absolute accomplishment. As long as you read this tutorial carefully and add some references when applying, mastering regular expressions is not a problem.
Many programming languages support string operations using regular expressions.
The following example finds the number from the string str:
Extract the content of the digital part from the string str (match once):
The text marked below is the matching expression obtained: