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

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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