How do I insert a blank line every n lines using awk?

Question

I've got an input file like this:

line 1
line 2
line 3
line 4
line 5
line 6

I'd like to use awk to insert a blank line every few lines; for example, every two:

line 1
line 2

line 3
line 4

line 5
line 6

How can I get awk to put a blank line into my file every n lines?

Answer 1

A more "awk-ish" way to write smcameron's answer:

awk -v n=5 '1; NR % n == 0 {print ""}'

The "1;" is a condition that is always true, and will trigger the default action which is to print the current line.

Answer 2

awk '{ if ((NR % 5) == 0) printf("\n"); print; }'

for n == 5, of course. Substitute whatever your idea of n is.

Answer 3

awk '{print; if (FNR % 5 == 0 ) printf "\n";}' your_file

I guess 'print' should be before 'printf', and FNR is more accurate for your task.

Answer 4

More awkishness:

awk 'ORS=NR%5?RS:RS RS'

For example:

$ printf "%s\n" {1..12} | awk 'ORS=NR%5?RS:RS RS'
1
2
3
4
5

6
7
8
9
10

11
12

Answer 5

$ awk -v n=5 '$0=(!(NR%n))?"\n"$0:$0'

If you want to change 'n', please set the parameter 'n' by awk's -v option.