How to get field value in logstash?

Elastic Stack Logstash
1

from my output as below,

"message" =>"<....... ",
"@version" => "1",
"@timestamp" => "2016-04-29T02:33:34.586Z",
"timestamp" => "Apr 29 10:30:37",
"syslog_severity_code" => 5,
"syslog_facility_code" => 1,
"syslog_facility" => "user-level",
"syslog_severity" => "notice"
i try to get the field value

filter
 {
     mutate {
     add_field => {"newfield"=> "timestamp"}
  }

but still cann't get the timestamp value to newfield it's will get

"newfield" => "newfield",

Is anyone is having the same problem or find a solution?
Any help is welcome to resolve this

2

Maybe you should read the logstash reference first:
https://www.elastic.co/guide/en/logstash/current/event-dependent-configuration.html

3 
 add_field => {"newfield"=> "timestamp"}

To copy the contents of the timestamp field to newfield you need this:

 add_field => {"newfield"=> "%{timestamp}"}
4

i have tried the cmd

add_field => {"newfield"=> "%{timestamp}"}

but It's strange , it's still can't get the timestamp value.
get results as follow,

 newfield => %{timestamp}

Is anyone is having the same problem or find a solution?
Any help is welcome to resolve this

5

If newfield ends up containing "%{timestamp}" then there was to timestamp field in the event. If you show us a complete example of your configuration, the input messages, what you actually get, and what you'd like to get it'll be easier to help out.