Regex with exclusion chars and another regex

Question

How to write regex which find word (without whitespace) that doesn't contain some chars (like * or #) and sentence also (like level10 or level2 - it should be also regex - level[0-9]+). It will be simple for chars excluded ([^\\s^#^*]+) but how to exclude this 'level' example too ?

I want to exclude chars AND level with number.

1. Examples:
   • weesdlevel3fv - shouldn't match because of 'level3'
   • we3rlevelw4erw - should match - there is level without number
   • dfs3leveldfvws#3vd - shouldn't match - level is good, but '#' char appeared
   • level4#level levelw4_level - threat as two words because of whitespaces - only second one should match - no levels with number and no restricted chars like '#' or '*'

Garbo

Please give more examples of valid and invalid input, and show what you tried. – Santamaria

Answer 1

See this regex:

/(?<=\s)(?!\S*[#*])(?!\S*level[0-9])\S+/

Regex explanation:

• (?<=\s) Asserts position after a whitespace sequence.
• (?!\S*[#*]) Asserts that "#" or "*" is absent in the sequence.
• (?!\S*level[0-9]) Asserts that level[0-9] is not matched in the sequence.
• \S+Now that our conditionals pass, this sequence is valid. Go ahead and use \S+ or \S++ to match the entire sequence.

To use lookaheads more exclusively, you can add another (?!\S*<false_to_assert>) group.

View a regex demo!

---

For this specific case you can use a double negation trick:

/(?<=\s)(?!\S*level[0-9])[^\s#*]+(?=\s)/

Another regex demo.

---

Read more:

• Regex for existence of some words whose order doesn't matter

Chazan

Thanks for answer and explanation. I tried it at 'weesdlevel3fv we3rlevel4erw dfsdfv#levels3vd fvlevels3vd' - should match last word but match last 3 – Garbo

@Garbo In regex, a word is defined as a collection of \w (word characters [A-Za-z0-9_]) surrounded by \W (non-word characters). I assume you meant that you are looking to match non-whitespace sequences (\S) between whitespaces (\s) then? – Chazan

+1 for efficient use of classic password validation technique. – Eczema

Answer 2

you can simply OR the searches with the pipe character [^\s#*]+|level[0-9]+

Rashad