Regex to include alphanumeric and _

Question

I\'m trying to create a regular expression to match alphanumeric characters and the underscore _. This is my regex: \"\\w_*[^-$\\s\\]\" and my impressi

Answer 1

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.

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

[\w_]

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

^[\w_]$

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_]+$

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

^[\w]+$

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

^\w+$

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