rotate log implementation by sh script

rotatelog.sh

#!/bin/sh
# Usage: rotatelog.sh [-zcn] level logfiles...

while getopts zcn flag; do
  case $flag in
  z) compress="/usr/bin/gzip"; ext=".gz";;
  c) compress="/usr/bin/compress"; ext=".Z";;
  n) ECHO="echo";
  esac
done
shift `expr $OPTIND - 1`; n=$1; shift
for file in $*; do
  n1=$n
  while [ $n1 -gt 1 ]; do
    n2=`expr $n1 - 1`
    $ECHO mv $file.$n2$ext $file.$n1$ext
    n1=$n2
  done
  $ECHO cp $file $file.1; $ECHO cp /dev/null $file
  [ $compress ] && $ECHO $compress $file.1
done