Question

Suppose to feed the filter standard input with these line:

line 1  line 2 line 3 line 4  line 5 line 6 line 7 line 8 line 9 line 10 

It would be nicer if someone tell me how to write a script that prints only every 4 lines, in the case of the example input above:

line 1 line 5 line 9 

Answer 1

$ yes | cat -n | head -10 | awk 'NR % 4 == 1'      1  y      5  y      9  y 

That is, your answer is ‘awk 'NR % 4 == 1'‘.