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

This will remove the last 3 lines from file:

for i in $(seq 1 3); do sed -i '$d' file; done;

Answer 2

To delete last 4 lines:

$ nl -b a file | sort -k1,1nr | sed '1, 4 d' | sort -k1,1n | sed 's/^ *[0-9]*\t//'   

Answer 3

A funny & simple sed and tac solution :

n=4
tac file.txt | sed "1,$n{d}" | tac

NOTE

• double quotes " are needed for the shell to evaluate the $n variable in sed command. In single quotes, no interpolate will be performed.
• tac is a cat reversed, see man 1 tac
• the {} in sed are there to separate $n & d (if not, the shell try to interpolate non existent $nd variable)

Answer 4

From the sed one-liners:

# delete the last 10 lines of a file
sed -e :a -e '$d;N;2,10ba' -e 'P;D'   # method 1
sed -n -e :a -e '1,10!{P;N;D;};N;ba'  # method 2

Seems to be what you are looing for.

Answer 5

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

Answer 6

Most of the above answers seem to require GNU commands/extensions:

    $ head -n -2 myfile.txt
    -2: Badly formed number

For a slightly more portible solution:

     perl -ne 'push(@fifo,$_);print shift(@fifo) if @fifo > 10;'

OR

     perl -ne 'push(@buf,$_);END{print @buf[0 ... $#buf-10]}'

OR

     awk '{buf[NR-1]=$0;}END{ for ( i=0; i < (NR-10); i++){ print buf[i];} }'

Where "10" is "n".