hi
if you want to redirect a partial data, you can try these commands
head -1000 oldfile >> newfile
and if u want to extract data from a middle of file, you can try the ombination of head and tail or you can try below
sed '12,36!d' oldfile >> newfile
or
sed '12,36p' oldfile >> newfile
Above commands will extract the lines from 12 to 36 from oldfile and append it into new file
try both above commands as I am not very much sure about which from above sed command runs , as i dont remember much , but you can give a try above
Thanks
Gaurav