Go to the list of seismic processes.      Go to SIOSEIS introduction. 

Script to decimate the seismic line by keeping every fourth trace.



procs diskin diskoa end
diskin
   ipath fdm.line6.2 fno 6001 lno 99999  noinc 4 end
end
diskoa
   fon 1 opath fdm.line6.2x4 end
end
prout
    fno 0 lno 999999 ftr 1 ltr 1 end
end
end