如何防止在正则表达式正则表达式验证空白 [英] how to prevent white spaces in a regular expression regex validation

问题描述

我对正则表达式是全新的，我试图在flex中为正则表达式创建一个正则表达式。

使用正则表达式，我将验证用户输入不包含任何空格，并且只包含字符和数字...以数字开头。

到目前为止我有：

 表达式=[A- Za-z] [A-Za-z0-9] *
  

正确检查用户输入开始一个字符后面跟一个可能的数字，但是这不检查是否有空白...（在我的测试中，如果用户输入有一个空间，这个输入将通过验证 - 这是不期望的）有人可以告诉我我怎样才能修改这个表达式，以确保用户输入与空白被标记为无效？

解决方案

您需要锚定正则表达式在字符串的开头和结尾：

$ $ $ $ $ $ $ $ $ $表达式=^ [A-Za-z] [A-Za- z0-9] * $

确保不只是一个子字符串，而是整个字符串匹配正则表达式。

I am completely new to regular expressions ,and I am trying to create a regular expression in flex for a validation.

Using a regular expression, I am going to validate that the user input does NOT contain any white-space and consists of only characters and digits... starting with digit.

so far i have:

expression="[A-Za-z][A-Za-z0-9]*"

This correctly checks for user input to start with a character followed by a possible digit, but this does not check if there is white space...(in my tests if user input has a space this input will pass through validation - this is not desired) can someone tell me how I can modify this expression to ensure that user input with whitespace is flagged as invalid?

解决方案

You'll need to anchor the regex at the start and end of the string:

expression="^[A-Za-z][A-Za-z0-9]*$"

makes sure that not just a substring but the entire string is matched by the regex.

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