#!/bin/sh
#
# rotate_files

if [ $# -ne 2 ] ; then
    echo "usage:  $0 filename num" >&2
    exit 1
fi

filename=$1
num=$2
if [ $num -lt 1 ] ; then
    echo "$0: number of files to keep must be at least 1" >&2
    exit 1
fi

rm -f $filename.$num

while [ $num -gt 1 ] ; do
    minus1=`echo $num - 1 | bc`
    if [ -f $filename.$minus1 ] ; then
	mv $filename.$minus1 $filename.$num
    fi
    num=$minus1
done

if [ -f $filename ] ; then
    mv $filename $filename.1
fi
touch $filename
