Question

What is the regex to allow dashes and numbers only?

A good example is use in a phone number. e.g. 555-555-555, 12-2314-425.

I don’t want entries like: ------------- though but -34--53-343 is fine for now.

Answer 1

So in the problem as stated, you want at least one digit but otherwise any of 0-9 or dash.

/^[\d-]*\d[\d-]*$/

%w{555-555-555 12-2314-425 -34--53-343 -------------}.each{|s| puts "#{s} #{s.match(/^[\d-]*\d[\d-]*$/) ? 'does' : 'does not'} match"}

555-555-555 does match
12-2314-425 does match
-34--53-343 does match
------------- does not match

If you’re trying to recognize phone numbers, you probably want something that recognizes sequences of digits optionally separated by single dashes, try this instead:

/^\d+(?:-\d+)*$/

Which excludes leading or trailing dashes and doubled dashes.