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This article is about how greedy patterns and lazy patterns are used in regular expressions. The editor thinks it is very practical, so share it with you as a reference and follow the editor to have a look.

Regular expressions greedy matching patterns, for beginners, are often easy to make mistakes. Sometimes you need to match the contents of a piece of code and find that the match is not consistent with what you want. It turns out that it has something to do with the pattern of greed. As follows, let's look at an example:

What is the mode of greed?

The string is: "abdbcd", we want to match... Content, the regular expression is as follows:

1. The beginning and end of h4, "to be added" are used as ordinary characters.

2. Any character can appear in the middle, the number can be 0 or more, and the regular expression can use:. *, "." Represents any character, the default pattern does not match line breaks, and "*" repeats 0 or more of the previous characters.

3. In the end, we consider that the result will be: ". *", or it can be: ". {0,}" {} represents, repeat the number of characters specified above, the following is used, regular expression debugging tool screenshot, the software can see: regular expression tool recommendation (learning tools, testing tools)

Both results are the same, which we don't want, we want to start on the left, the first one to appear, and then we start to match. The above pattern is greedy, and regular expressions are matched by default. Represents repeating characters, operators, the default is greedy mode, such as:. *,. +,. {1,},. {0,} will match the maximum length characters. Regular expression metacharacters, quantifiers default to the first maximum match string, these quantifiers are: +, *,?, {mforce n}. As soon as the match starts, it matches directly to the longest string.

What is the lazy mode?

Since the above indicates the number of repeated characters, metacharacters are greedy by default. If we need a minimum length match, that is, a lazy pattern, how do we write regular expressions? In fact, the common method in regular expressions is to represent repeating metacharacters, followed by an extra "?" Characters are fine. The above regular expression can be written as ". *?" or ". {0,}?" All are fine.

The lazy pattern matches to the point where we need a string.

Thank you for reading! This is the end of the article on "how to use greedy patterns and lazy patterns in regular expressions". I hope the above content can be helpful to you, so that you can learn more knowledge. If you think the article is good, you can share it for more people to see!

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