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?
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?
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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