How to match strings that are entirely composed of a predefined set of substrings. For example, I want to see if a string is composed of only the following allowed substrings:

• ,
• 034
• 140
• 201

In the case when my string is as follows:

034,201

The string is fully composed of the 'allowed' substrings, so I want to positively match it. However, in the following string:

034,055,201

There is an additional 055, which is not in my 'allowed' substrings set. So I want to not match that string.

What regex would be capable of doing this?

CodePudding user response：

Try this one:

^(034|201|140|,) $

Here is a demo

Step by step:

• ^ begining of a line
• (034|201|140|,) captures group with alternative possible matches
• captured group appears one or more times
• $ end of a line

CodePudding user response：

This regex will match only your values and ensure that the line doesn't start or end with a comma. Only matches in group 0 if it is valid, the groups are non-matching.

^(?:034|140|201)(?:,(?:034|140|201))*$

• ^: start
• (?:034|140|201): non-matching group for your set of items (no comma)
• (?:,(?:034|140|201))*: non-matching group of a comma followed by non-matching group of values, 0 or more times
• $: end