fixed length look-behind in RegEx

Asked Aug 20 '18 at 11:58

Active Aug 20 '18 at 11:58

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I'm trying to extract a number from a string. The string is randomized but must contain one keyword, let's say 'key', and a number. I want to extract the first number behind the keyword.

Below is a sample string:

123samples45have'key'andnumber678and90

So in this sample string, number 678 is required.

I write the expression like (?<=key.*?)[0-9]+, but it appears Ruby only support fixed length look-behind. Is there any other solution could solve this?

asked Aug 20 '18 at 11:58

Fingalzzz

`s[/key.*?([0-9]+)/, 1]` or `s[/key.*?\K[0-9]+/]` will do. – Wiktor Stribiżew Aug 20 '18 at 12:00
Or `(?<=key)\D+\K\d+`. – Paolo Aug 20 '18 at 12:01

fixed length look-behind in RegEx

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