Regular expression usage of arbitrary characters

Regular expression arbitrary character usage includes dot (.), character class ([ ]), excluded character class ([^]), wildcard (*), plus sign (+), question mark (?), greedy mode and non-greedy mode , newline matching. Detailed introduction: 1. The dot sign (.), the dot sign means matching any character, except the newline character. For example, the regular expression "a.b" can match "axb", "ayb", "azb", etc.; 2. Character class ([ ]), the character class is used to match any character in a set of characters, etc.