backup

#!/bin/bash -e
file='File'
if [[ -e ${file}.3 ]]; then mv ${file}.3 ${file}.4; fi
if [[ -e ${file}.2 ]]; then mv ${file}.2 ${file}.3; fi
if [[ -e ${file}.1 ]]; then mv ${file}.1 ${file}.2; fi
if [[ -e ${file} ]]; then mv ${file} ${file}.1; fi
:>${file}