How to add a 0 before a field, with a condicion?

Elastic Stack Logstash
1

Hello!
I have different docs with different hours from 0 to 23 like the following
{
"date" : "2022-06-23",
"eventDate" : "2022",
"StoreID" : 190,
"hour" : 0,
"PosID" : 12,
"tempo" : 0.0
}
{
"date" : "2022-06-23",
"eventDate" : "2022",
"StoreID" : 190,
"hour" : 1,
"PosID" : 12,
"tempo" : 0.0
}
For the field hour, i need to add a 0 before the number if its below 10.
I tried different methods like this:
ruby {
code => '
if event.get('hour') =~ /^\d{1}$/
event.set('hour', '0'+event.get('hour'))
end
'
}
but gives me an error
What can I do?

2

If you use single quotes to surround the code then within the code you must use double quotes.