Regex - Match only letters, numbers, and one space between each word

Question

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

Good Examples:

Amazing

Hello Beautiful World

I am 13 years old

Bad Examples:

Hello  world

I am 13 years      old.

I    am   Chuck Norris

Answer 1

This would match a word

'[a-zA-Z0-9]+\ ?'

Answer 2

([a-zA-Z0-9]+ ?)+?

Answer 3

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.

Answer 4

^[a-zA-Z]+([\s][a-zA-Z]+)*$