Shell Script To Delete All Even Numbered Line From a Text File

in Categories Academic, Decision Making, File-management last updated September 17, 2008

Shell Script To Delete All Even Numbered Line From a Text File

#!/bin/bash
# Write a shell script which deletes all even numbered line from a text file.
# -------------------------------------------------------------------------
# Copyright (c) 2008 nixCraft project <http://cyberciti.biz/fb/>
# This script is licensed under GNU GPL version 2.0 or above
# -------------------------------------------------------------------------
# This script is part of nixCraft shell script collection (NSSC)
# Visit http://bash.cyberciti.biz/ for more information.
# -------------------------------------------------------------------------
 
file=$1
counter=0
 
out="oddfile.$$" # odd file name
 
if [ $# -eq 0 ] 
then
	echo "$(basename $0) file"
	exit 1 
fi
 
if [ ! -f $file ]
then
	echo "$file not a file!"
	exit 2
fi
 
while read line
do
	# find out odd or even line number 
	isEvenNo=$( expr $counter % 2 )
 
	if [ $isEvenNo -eq 0 ] 
	then
		# odd match; copy all odd lines $out file
		echo $line >> $out
	fi
	# increase counter by 1
	(( counter ++ ))
done < $file
# remove input file
/bin/rm -f $file
 
# rename temp out file 
/bin/mv $out $file

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4 comment

  1. @Kiat Huang

    for some reason your simplified command does not work on my mac. But the following works like a charm.

    for even lines
    sed -e ‘1d;n;d’ yahoo.txt

    for odd lines
    sed -e ‘2d;n;d’ yahoo.txt

  2. I want to combine to text file in unix. Both text files have 100 lines each, i want to only take the 1st 60 line from the 1st file and combine it with the 2nd file.

    How do i do that?

  3. # This does the same thing quicker and with greater flexibility

    # e.g. delete every 2nd line starting from the 0th line
    sed ‘0~2d’ -i $file

    # e.g. delete every 2nd line starting from the 1st line
    sed ‘1~2d’ -i $file

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