Logstash - Grok - Parse Digit

[pjo]

Hello,

I have this simple chain that represent a date (with 2digit year format)

200424

I'm looking for a way to parse it to obtain this output :

year : 20
month : 04
montday : 24

Is it possible with grok to extract part of a string / digit based on start/end position (like php function substr) ?

Thanks

[pjo]

it look this do the job with regexp rather than grok pattern

(?<year>([12]\d{1}))(?<month>(0[1-9]|1[0-2]))(?<monthday>(0[1-9]|[12]\d|3[01]))