Regular expression to match specific words seperated by spaces

Question

I have a list of say 5 words (foo bar foobar footable somebar). This list of words will be provided as a string each separated by space and in any order. I need a regex matching below requirements

1. inputted string should contain only the 5 above mentioned words
2. each word separated by space
3. each word only once
4. regex should match the entire string - if any portion does not match above criteria, it should be failed match

So far I have this (\b(foo|bar|foobar|footable|somebar)\b\ *){1,5}

1. Matches only the mentioned words
2. Words separated by space

Need a solution for the 3rd & 4th requirements

3. each word only once
4. regex should match the entire string - if any portion of the string does not match above criteria, it should be a failed match

Answer 1

Start with a regular expression that matches exactly 5 words:

^(?:\w+\s+){4}\w+$

The anchors ensure that this matches the entire string.

Then prefix this with lookaheads that match each of the words.

(?=.*\bfoo\b)(?=.*\bbar\b)(?=.*\bfoobar\b)(?=.*\bfootable\b)(?=.*\bsomebar\b)^(?:\w+\s+){4}\w+$

DEMO