replace older package version name to newer one

replace.sh

#!/bin/bash
OLD="xenial"
NEW="zesty"
DPATH="/etc/apt/sources.list*"
BPATH="./play/"
TFILE="./play/out.tmp"
[ ! -d $BPATH ] && mkdir -p $BPATH || :
for f in $DPATH
do
  if [ -f $f -a -r $f ]; then
   /bin/cp -f $f "$BPATH/$(basename $f)"
   sed "s/$OLD/$NEW/gi" "$f" > $TFILE && mv $TFILE "$(basename $f)"
  else
   echo "Error: Cannot read $f"
  fi
done
/bin/rm $TFILE