How can I delete every Xth line in a text file?

Question

Consider a text file with scientific data, e.g.:

5.787037037037037063e-02 2.048402977658663748e-01
1.157407407407407413e-01 4.021264347118673754e-01
1.736111         


        

Answer 1

This is easy to accomplish with awk.

Remove every other line:

awk 'NR % 2 == 0' file > newfile

Remove every 10th line:

awk 'NR % 10 != 0' file > newfile

The NR variable in awk is the line number. Anything outside of { } in awk is a conditional, and the default action is to print.