use the -n option of sed, for example:

sample file link.txt contains:
text
http://www.google.com
text
http://www.unix.com
last line

filter file link.flt contains:
1,$ {
/http:\/\// {
p
}
}

$ sed -n -f link.flt link.txt
http://www.google.com
http://www.unix.com
$