从字符串中获取一个恰好x位数字的数字 [英] Get a number with exactly x digits from string

问题描述

我正在寻找一个正则表达式模式，该模式与长度恰好为x的数字(例如x为2-4)匹配，并且没有其他匹配项.

im looking for a regex pattern, which matches a number with a length of exactly x (say x is 2-4) and nothing else.

示例:

"foo.bar 123 456789"，"foo.bar 456789 123"，" 123"，"foo.bar123 "只必须匹配"123"

"foo.bar 123 456789", "foo.bar 456789 123", " 123", "foo.bar123 " has to match only "123"

所以.只能是数字，不能有空格，字母或其他东西.

So. Only digits, no spaces, letters or other stuff.

我该怎么做?

我想在c#中使用Regex.Matches()函数提取此2-4位数字，并在其他代码中使用它.

I want to use the Regex.Matches() function in c# to extract this 2-4 digit number and use it in additional code.

推荐答案

后跟{m,n}的任何模式都允许该模式发生m到n次.因此，对于您所需的m和n值，在\d{m,n}中.如果必须完全是整数，请使用\d{m}

Any pattern followed by a {m,n} allows the pattern to occur m to n times. So in your case \d{m,n} for required values of m and n. If it has to be exactly an integer, use\d{m}

如果要在x123y中匹配123，而不要在1234中匹配，请使用\d{3}(?=\D|$)(?<=(\D|^)\d{3})

If you want to match 123 in x123y and not in 1234, use \d{3}(?=\D|$)(?<=(\D|^)\d{3})

前瞻性地确保3位数字之后的字符完全不是数字，而后方确保3位数字之前的字符完全是非数字或什么都没有.

It has a look ahead to ensure the character following the 3 digits is a non-digitornothing at all and a look behind to ensure that the character before the 3 digits is a non-digit or nothing at all.

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