Print Nth Line of File#

$ sed -n '10p' file

This prints line number 10.

Ranges are also possible:

$ sed -n '3,5p' infile

prints lines 3, 4 and 5.

Print Every Nth Line of File#

To print lines 1, 11, 21, etc do

$ awk '{if (count++%10==0) print $0;}' input_file

To print lines 10, 20, 30, etc do

$ awk '{if (++count%10==0) print $0;}' input_file

You can also use the following to print every 5th line starting at line 2. This doesn't appear to work for me on Mac.

$ sed -n '2~5p' input_file

To