如何使正则表达式的一部分成为可选的? [英] How can I make part of regex optional?

问题描述

假设我有以下正则表达式匹配末尾带有分号的字符串:

Suppose I have the following regex that matches a string with a semicolon at the end:

\".+\";

它将匹配除空字符串之外的任何字符串，如下所示:

It will match any string except an empty one, like the one below:

"";

我试过用这个:

\".+?\";

但这没有用.

我的问题是，如何使 .+ 成为可选的一部分，以便用户不必在字符串中放入任何字符?

My question is, how can I make the .+ part of the, optional, so the user doesn't have to put any characters in the string?

推荐答案

要使 .+ 成为可选项，您可以这样做:

To make the .+ optional, you could do:

\"(?:.+)?\";

(?:..) 被称为 非捕获组.它只执行匹配操作，不会捕获任何内容.在非捕获组之后添加 ? 使整个非捕获组可选.

(?:..) is called a non-capturing group. It only does the matching operation and it won't capture anything. Adding ? after the non-capturing group makes the whole non-capturing group optional.

或者，您可以这样做:

\".*?\";

.* 会贪婪地匹配任何字符零次或多次.在 * 之后添加 ? 强制正则表达式引擎进行尽可能短的匹配.

.* would match any character zero or more times greedily. Adding ? after the * forces the regex engine to do a shortest possible match.

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