1. Regular expressions
1. A regular expression is a formula for matching strings according to a certain template, which consists of ordinary characters (such as characters a to z) and special characters.
(1) Ordinary characters: the matched object is the ordinary characters themselves.
Includes all uppercase and lowercase letters, numbers, punctuation marks, and some special symbols. For example: a matches a in abc, 10 matches 10 in 10.113.25.155, @ matches @ in [email protected].
(2) Special characters: match complex or special string combinations with ordinary characters
Stand-alone control characters or placeholders that precede or follow ordinary characters to limit or expand ordinary characters. Used to describe how the character preceding it is repeated. Limit a complete range.
Type 1
Type 1 example:
^a.$: Matches a string that starts with the character a and ends with any single character, such as a0, a!, ax, etc.