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

I came up with this, where n is the number of lines you want to delete:

count=`wc -l file`
lines=`expr "$count" - n`
head -n "$lines" file > temp.txt
mv temp.txt file
rm -f temp.txt

It's a little roundabout, but I think it's easy to follow.

1. Count up the number of lines in the main file
2. Subtract the number of lines you want to remove from the count
3. Print out the number of lines you want to keep and store in a temp file
4. Replace the main file with the temp file
5. Remove the temp file