How to use sed to remove the last n lines of a file

Question

I want to remove some n lines from the end of a file. Can this be done using sed?

For example, to remove lines from 2 to 4, I can use

$ sed          


        

Answer 1

It can be done in 3 steps:

a) Count the number of lines in the file you want to edit:

 n=`cat myfile |wc -l`

b) Subtract from that number the number of lines to delete:

 x=$((n-3))

c) Tell sed to delete from that line number ($x) to the end:

 sed "$x,\$d" myfile