Home  >  Article  >  What are the regular expression quantifiers?

What are the regular expression quantifiers?

小老鼠
小老鼠Original
2023-11-20 17:00:421164browse

Regular expression quantifiers include:, ,?,{n},{n,},{n,m},?, ,*, etc. Detailed introduction: 1.: Indicates matching the previous element 0 or more times. For example, ab can match a or ab or abbb, etc.; 2. : means matching the previous element one or more times. For example, ab can match ab or abbb, etc.; 3. ?: means matching the previous element 0 or 1 times. For example, ab? can match a or ab; 4. {n}: means matching the previous element exactly n times. For example, a{2} can match aa and so on.

What are the regular expression quantifiers?

Operating system for this tutorial: Windows 10 system, Dell G3 computer.

Regular expression quantifiers are special symbols used to specify the number of matches. The following are common regular expression quantifiers:

  1. : Indicates matching the previous element 0 or more times. For example, ab can match a or ab or abbb, etc.

  2. : Indicates matching the previous element one or more times. For example, ab can match ab or abbb, etc.

  3. ?: Indicates matching the previous element 0 or 1 times. For example, ab? matches a or ab.

  4. {n}: Indicates matching the previous element exactly n times. For example, a{2} matches aa.

  5. {n,}: Indicates matching the previous element at least n times. For example, a{2,} can match strings such as aa, aaa, aaaa, etc.

  6. {n,m}: Indicates matching the previous element at least n times, but not more than m times. For example, a{2,3} can match aa, aaa, but not aaaa.

  7. ?: Indicates matching the previous element 0 or 1 times. For example, [0-9]? can match 0 or 1 number.

  8. : Indicates matching the previous element one or more times. For example, [0-9] can match 1 or more numbers.

  9. *: Indicates matching the previous element 0 or more times. For example, [0-9]* can match 0 or more numbers.

These quantifiers can be used to specify the number of repetitions of characters in a regular expression, allowing for more precise pattern matching. Note that different regular expression engines may support different quantifier syntax and functionality.

The above is the detailed content of What are the regular expression quantifiers?. For more information, please follow other related articles on the PHP Chinese website!

Statement:
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn