append to fle using sed



hello ,

i have the folloiwing command :
sed -n "$var,$final w $destfile" $sourcefile

where :
$var - $final represent the range of line numbers to be written in $destfile


however i require this command to work in a loop for which i need the sed command to keep appending the output to the $destfile .

any help ??
thanks in advance ,

sd,
"sed" overwrites the file in the "w" option every time it runs.
if you want to continue appending to the file, you can try
this alternate "sed" solution:

code:

rm -f ${sourcefile}