To print a line at a given position (say, line 10) within a file, we can use this invocation of sed:
sed'10q;d'file
d means every line will be removed from the output, except for line 10, where the deletion is short-circuited by quitting q. The result is that only line 10 is printed, and the rest of the file isn't processed.
An alternative is:
sed-n'10p'file
It is somewhat more intuitive, using -n to avoid printing lines, except for line 10 which is explicitly printed. The drawback is that the entire file is processed. Keep this in mind if performance is a priority.