正则表达式包含字母数字和 _ [英] Regex to include alphanumeric and _

问题描述

我正在尝试创建一个正则表达式来匹配字母数字字符和下划线 _.这是我的正则表达式:"\w_*[^-$\s\]" 我的印象是这个正则表达式表示任何字母数字字符 \w，下划线 _，并且没有 -、$ 或空格.这是正确的吗?

I'm trying to create a regular expression to match alphanumeric characters and the underscore _. This is my regex: "\w_*[^-$\s\]" and my impression is that this regex means any alphanumeric character \w, an underscore _, and no -,$, or whitespace. Is this correct?

推荐答案

正则表达式被读作实际匹配字符串中字符的模式，从左到右，因此您的模式实际上匹配一个字母数字，然后是下划线(0 或更多), THEN 至少有一个不是连字符、美元或空格的字符.

Regular expressions are read as patterns which actually match characters in a string, left to right, so your pattern actually matches an alphanumeric, THEN an underscore (0 or more), THEN at least one character that is not a hyphen, dollar, or whitespace.

由于您尝试更改字符类型，因此只需使用字符类来显示您允许使用的字符:

Since you're trying to alternate on character types, just use a character class to show what characters you're allowing:

[\w_]

这会检查字符串的任何部分是否与它匹配，因此让我们将其锚定到字符串的开头和和:

This checks that ANY part of the string matches it, so let's anchor it to the beginning and and of the string:

^[\w_]$

现在我们看到字符类缺少量词，所以我们只匹配一个字符.我们可以使用 +(如果你想要一个或多个字符，没有空字符串)或 *(如果你想允许空字符串)来解决这个问题.我将在这里使用 +.

And now we see that the character class lacks a quantifier, so we are matching on exactly ONE character. We can fix that using + (if you want one or more characters, no empty strings) or * (if you want to allow empty strings). I'll use + here.

^[\w_]+$

事实证明，\w 字符类已经包含下划线，因此我们可以从模式中删除多余的下划线:

As it turns out, the \w character class already includes the underscore, so we can remove the redundant underscore from the pattern:

^[\w]+$

现在我们在字符类中只有一个字符，所以我们根本不再需要字符类括号:

And now we have only one character in the character class, so we no longer need the character class brackets at all:

^\w+$

这就是您所需要的，除非我遗漏了您的要求.

And that's all you need, unless I'm missing something about your requirements.

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