Logstash out put csv with header

[Yungyoung_Ok (ooyy)]

I am trying to create a csv file by using the output csv in logstash.
How can I insert the header only once at the very beginning?

my data:

    es_field1 es_field2 es_field3
    1               2              3
    4               5              6
    7               8              9

logstash config:

    output {
     path => "/my/path/to/csv"
     csv_options => {
      "write_headers" => true
      "hearders" => "a,b,c"
     } 
     fields => ["es_field1", "es_field", "es_field"]
    }

result:

    a b c
    1 2 3
    a b c 
    4 5 6
    a b c 
    7 8 9 

Headers are inserted for each row.
How can I insert the header only once at the very beginning?

[Badger]

@Yungyoung_Ok

How can I insert the header only once at the very beginning?

You cannot make the csv output do that. It is an open issue.