Fetch a value from diffrent field in NIFI

[#1]

"result" : "SUCCESS",
"correlationID" : "X8058296",
"generationTimestamp" : "1354",
"meHostName" : "rc01;rik2jc",
"nccVersion" : "SPS__R1",

This is my input in my nifi and i want to do changes in meHostName means i want mehostName to have 1st value like in this case rc01 and after that creating 1 more field with name devicename having second value means rik2jc

I acheived the 1st part means i configured in UpdateRecord processor 

for meHostName and it is printing 1st value means it is running fine ,now please help me in acheiving devicename to have 2nd value of meHostName which is rik2jc . i have tried split(/meHostName, ';')[1] but its not working

[#2]

@Ashi 
Potential option:

What record Reader and record writers are you using in your UpdateRecord processor?
What schema are you using for your records?

In order to add a new field, that new field needs to be defined in the records schema. 
In your case the schema must contain the field "devicename".
Prior to UpdateRecord, you could use perhaps an ExtractText processor to extract the "rc01;rik2jc" value from the meHostName field to a flowfile.attribute.

Then will you be able to use UdpateRecord to apply a value to that new record field in the record writer.

Property: /devicename
value: ${flowfile.attribute:substringAfter(';')}

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Thank you,
Matt

[#3]

Record reader -JsonTreeReader

record writer - JsonRecordSetWriter this i am using in my update record and for reference this is my flow looks like