How to export http.data with tshark?

Hi,

I want to read tcpdump capture file and export just http request body as individual byte array. How to do that? I tried this

tshark -r mycapture.cap -R 'http.request and (http contains "customheader:")' -T fields -e data -w data.cap

But it save all the requests with headers (I just want the http body only). Also it doesn't save http body as individual file.

Thanks,