What regular expression can I use to find the Nᵗʰ entry in a comma-separated list?

Question

I need a regular expression that can be used to find the N^th entry in a comma-separated list.

For example, say this list looks like this:

abc,def,4322,[email protected],3321,alpha-beta,43

...and I wanted to find the value of the 7^th entry (alpha-beta).

Solution

My first thought would not be to use a regular expression, but to use something that splits the string into an array on the comma, but since you asked for a regex.

most regexes allow you to specify a minimum or maximum match, so something like this would probably work.

/(?:[^\,]*\,){6}([^,]*)/

This is intended to match any number of character that are not a comma followed by a comma six times exactly (?:[^,]*,){6} - the ?: says to not capture - and then to match and capture any number of characters that are not a comma ([^,]+). You want to use the first capture group.

Let me know if you need more info.

EDIT: I edited the above to not capture the first part of the string. This regex works in C# and Ruby.

Comments

[gymbrall]

I believe this also works in Java, though you may need to use the group property and it would be the second element in the group array.