正则表达式匹配 0 - 999 但不为空 [英] Regex to match 0 - 999 but not blank

问题描述

我正在研究一个正则表达式来匹配有效的整数，例如:

I'm working on a regex to match valid integer numbers such as the following:

• 0
• 1
• 99
• 999

但是它不应该允许匹配空字符串.我能得到的最接近的是:

However it should not allow matching an empty string. The closest I can get is:

(0)|\\d{1,3}

对我来说，匹配的字符串将包含一个零或一系列长度介于 1 到 3 个字符之间的数字.但是，空字符串似乎仍与此模式匹配.从这个正则表达式中排除空字符串的正确方法是什么?

Which to me says a matching string will have either a zero or a series of digits between 1 and 3 characters long. However, empty strings still appear to match this pattern. What's the proper way to exclude empty strings from this regex?

推荐答案

这将匹配(仅)一系列一到三个数字(包括 0 或 00 或 01 或 012 - 不清楚是否需要后者):

This will match (only) a series of one to three numeric digits (including 0 or 00 or 01 or 012 - not clear if those latter ones are desired):

^\d{1,3}$

它不会匹配空字符串(但你原来的复杂表达式也不会).

It will not match empty string (but then neither will your original convoluted expression).

(要允许它作为更大字符串的一部分，请删除 ^ 和 $ 锚点.)

(To allow this as part of a bigger string, remove the ^ and $ anchors.)

但也许正则表达式在这里不是最佳选择 - 您使用的任何基础语言都没有 isNumeric 函数吗?

But perhaps regex is not best option here - does whatever base language you're using not have an isNumeric function?

要允许 0 但不允许其他以 0 为前缀的数字，您可以使用:

To allow 0 but not other 0-prefixed numbers, you can use:

0|[1-9]\d{0,2}

或者，确保这是整个匹配:

Or, to ensure that's the entire match:

^(?:0|[1-9]\d{0,2})$

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