One solution is to use a flocking command "flock()" or to use lock and unlock files. Both of these are good but neither guarantee 100% safety. Therefore I have developed two utilities that are easily used to backup files and restore lost data. It's not 100% guaranteed either but when used in conjunction with one of these other protection methods then it goes a long way to reducing most of the risk!

backup.pl : backup([file_abs_path])

This utility will take an existing file on your Unix server and make a backup copy of it. It creates a file with an identical name, in the same directory but the extension is changed to ".bak". I write in the program that every time a critical file is generated or updated, it also gets backed up. This backup utility requires only one parameter be passed to it. This parameter is the absolute path to the file that you want backed up.

restore.pl : @contents = restore([file_abs_path])

This utility, when called, will search the directory in question for a backup file (file same name but extension of ".bak"). If the backup file is found the utility then restores the original files contents as they were when it was last backed up. The program then returns from the subroutine the contents of the file.

As you can see, these two utilities were designed to be used to together but they don't have to be used together.

Here is an example of the backup of a file:

if(open(BITS, ">$DataPath/parts/catalogue.file")) {
    flock(BITS, '2');
    print BITS "$entry\n";
    close(BITS);
    backup("$DataPath/parts/catalogue.bak");
}

if you were using my 'fileadd.pl' utility then it would look like this:

fileadd("$DataPath/parts/catalogue.file", "$entry");
backup("$DataPath/parts/catalogue.file");

This will now make two files in the directory 'parts', they are:

if(open(BITS, "<$DataPath/parts/catalogue.file")) {
    flock(BITS, '2');
    @contents = ;
    close(BITS);
    if(!$contents[0]) {
	@contents = restore("$DataPath/parts/catalogue.file");
    }
}

....or....

@contents = getfile("$DataPath/parts/catalogue.file");
if(!$contents[0]) {
    @contents = restore("$DataPath/parts/catalogue.file");
}