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

Use sed, but let the shell do the math, with the goal being to use the d command by giving a range (to remove the last 23 lines):

sed -i "$(($(wc -l < file)-22)),\$d" file

To remove the last 3 lines, from inside out:

$(wc -l < file)

Gives the number of lines of the file: say 2196

We want to remove the last 23 lines, so for left side or range:

$((2196-22))

Gives: 2174 Thus the original sed after shell interpretation is:

sed -i '2174,$d' file

With -i doing inplace edit, file is now 2173 lines!

If you want to save it into a new file, the code is:

sed -i '2174,$d' file > outputfile