I want a regular expression that prevents symbols and only allows letters and numbers. The regex below works great, but it doesn't allow for spaces between words.
^[a-zA-Z0-9_]*$
For example, when using this regular expression "HelloWorld" is fine, but "Hello World" does not match.
How can I tweak it to allow spaces?
Just add a space in your character class.
^[a-zA-Z0-9_ ]*$
The above isn't exactly correct. Due to the fact that *
means zero or more, it would match all of the following cases that one would not usually mean to match:
Originally I didn't think such details were worth going into, as OP was asking such a basic question that it seemed strictness wasn't a concern. Now that the question's gained some popularity however, I want to say...
Which, in my flavor (without using \w
) translates to:
^[a-zA-Z0-9_]+( [a-zA-Z0-9_]+)*$
(Please upvote @stema regardless.)
Some things to note about this (and @stema's) answer:
If you want to allow multiple spaces between words (say, if you'd like to allow accidental double-spaces, or if you're working with copy-pasted text from a PDF), then add a +
after the space:
^\w+( +\w+)*$
If you want to allow tabs and newlines (whitespace characters), then replace the space with a \s+
:
^\w+(\s+\w+)*$
Here I suggest the +
by default because, for example, Windows linebreaks consist of two whitespace characters in sequence, \r\n
, so you'll need the +
to catch both.
Check what dialect of regular expressions you're using.* In languages like Java you'll have to escape your backslashes, i.e. \\w
and \\s
. In older or more basic languages and utilities, like sed
, \w
and \s
aren't defined, so write them out with character classes, e.g. [a-zA-Z0-9_]
and [\f\n\p\r\t]
, respectively.
* I know this question is tagged vb.net, but based on 25,000+ views, I'm guessing it's not only those folks who are coming across this question. Currently it's the first hit on google for the search phrase, regular expression space word.