What regex can I use to match only letters, numbers, and one space between each word?

Question

How can I create a regex expression that will match only letters and numbers, and one space between each word?

Good Examples:

Answer 1

Most regex implementations support named character classes:

^[[:alnum:]]+( [[:alnum:]]+)*$

You could be clever though a little less clear and simplify this to:

^([[:alnum:]]+ ?)*$

FYI, the second one allows a spurious space character at the end of the string. If you don't want that stick with the first regex.

Also as other posters said, if [[:alnum:]] doesn't work for you then you can use [A-Za-z0-9] instead.