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:

Answer 1

You could use something like:

([^,]*,){$m}([^,]*),

As a starting point. (Replace $m with the value of (n-1).) The content would be in capture group 2. This doesn't handle things like lists of size n, but that's just a matter of making the appropriate modifications for your situation.

Answer 2

@list = split /,/ => $string;
$it = $list[6];

or just

$it = (split /,/ => $string)[6];

Beats writing a pattern with a {6} in it every time.

Answer 3

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.