How do I delete the first n lines of an ascii file using shell commands?

If the tabulated lines are the ones that have a tab character:

grep '␉' <input_file >output_file

(␉ being a literal tab character) or equivalently

sed -n '/␉/p' <input_file >output_file

In a bash/ksh/zsh script, you can write $'t' for a tab, e.g. grep $'t' or sed -n $'/t/p'.

If you want to eliminate 10 lines at the beginning of the file:

tail -n +11 <input_file >output_file

(note that it’s +11 to eliminate 10 lines, because +11 means “start from line 11” and tail numbers lines from 1) or

sed '1,10d' <input_file >output_file

On Linux, you can take advantage of GNU sed’s -i option to modify files in place:

sed -i -n '/t/p' *.txt

Or you can use a shell loop and temporary files:

for x in *.txt; do
  tail -n +11 <"$x" >"$x.tmp"
  mv "$x.tmp" "$x"
done

Or if you don’t want to modify the files in place, but instead give them a different name:

for x in *.txt; do
  tail -n +11 <"$x" >"${x%.txt}.data"
done

You can use Vim in Ex mode:

ex -s -c '1d5|x' file

1. 1 move to first line

2. 5 select 5 lines

3. d delete

4. x save and close

sed -i '1,3d' file.txt

This deletes first 3 line from file.txt.

# deletes first line
echo "anb" | sed '1d' 

# read list.txt and write list.csv without first line
cat list.txt | sed '1d' > list.csv 

Other useful commands:

# finds first character (pipe|)
grep '^|' 

# deletes pipe
sed 's/|//g'  

# deletes space
sed 's/ //g' 

By percentage

Using bash, to clean up a file using a percentage number instead of an absolute number of lines:

sed -i -e 1,$( printf  "$((`cat php_errors.log | wc -l` * 75 /100 ))" )d php_errors.log

Watch out because that command can be destructive since it deletes content in-place, without creating a copy.

It deletes the first 75% of lines from the mentioned file.

i created a small script which will delete everything from the /var/log/messages except last 4 lines.

# cat remove-range-of-lines.sh

#!/usr/bin/bash

#print total line number
line_count=`awk 'END{print NR}' /var/log/messages`

#exclude last 4 lines
remove_line=`expr $line_count - 4`

#remove everything except last 4 lines
sed -i '1,'$remove_line'd' /var/log/messages

using this script we can always keep latest entry in the /var/log/messages based on our requirement

if you want to keep last 10000 entries in the /var/log/messages below is the modified script.

#!/usr/bin/bash

#print total line number
line_count=`awk 'END{print NR}' /var/log/messages`

#exclude last 10000 lines
remove_line=`expr $line_count - 10000`

#remove everything except last 10000 lines
sed -i '1,'$remove_line'd' /var/log/messages