Question

In an application I have the need to validate a string entered by the user.

One number
OR
a range (two numbers separated by a ‘-‘)
OR
a list of comma separated numbers and/or ranges
AND
any number must be between 1 and 999999.

A space is allowed before and after a comma and or ‘-‘.

I thought the following regular expression would do it.

(\d{1,6}\040?(,|-)?\040?){1,}

This matches the following (which is excellent). (\040 in the regular expression is the character for space).

• 00001
• 12
• 20,21,22
• 100-200
• 1,2-9,11-12
• 20, 21, 22
• 100 – 200
• 1, 2 – 9, 11 – 12

However, I also get a match on:

• !!!12

What am I missing here?

Answer 1

You need to anchor your regex

^(\d{1,6}\040?(,|-)?\040?){1,}$

otherwise you will get a partial match on “!!!12”, it matches only on the last digits.

See it here on Regexr