backup_file

#!/bin/bash

SRC_FILE_NAME="$1"

if [[ "$SRC_FILE_NAME" = "" ]] ; then
	echo "Usage: $0 FILE"
	exit
fi

if [[ ! -f "$SRC_FILE_NAME" ]] ; then
	echo "Not a regular file: $SRC_FILE_NAME"
	exit
fi

for TMP in {00..99}
do
	BAK_FILE_NAME="$SRC_FILE_NAME.bak$TMP"
	if [[ ! -e "$BAK_FILE_NAME" ]] ; then
		echo "Backing up file: $SRC_FILE_NAME ==> $BAK_FILE_NAME"
		
		cp --preserve=all -- "$SRC_FILE_NAME" "$BAK_FILE_NAME"
		if [[ "$?" == "0" ]] ; then
			chmod -x -- "$BAK_FILE_NAME"
		fi
		exit
	fi
done

echo "Can't find free file name: $SRC_FILE_NAME"