back up file for a single file

#!/bin/bash

if [ -z "$1" ]

  then

    echo "No argument supplied"

exit

fi

BASENAME1=$(/bin/basename $1)

MYPATH1=$(/bin/pwd)

backupdir="$MYPATH1/backupdir"

mydate=$(date +"%m-%d-%y-%N")

if [ ! -d "$backupdir" ]; then

    mkdir $backupdir

fi

cp $MYPATH1/$BASENAME1 $backupdir/$BASENAME1-$mydate