Nicola Worthington > Util-SelfDestruct-1.21 > Util::SelfDestruct



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Util::SelfDestruct - Conditionally prevent execution of a script


 # Immediately prevent execution of script by dying on invocation
 # if it has already been executed once before. (The default behavior
 # is to self destruct by dying, unless instructed otherwise).
 use Util::SelfDestruct;
 # Delete the script after it is executed
 use Util::SelfDestruct('unlink');
 # Prevent execution of the script by dying if it
 # is executed after Dec 17th 2005 at 6pm
 use Util::SelfDestruct(after => '2005-12-17 18h00m00s');
 # Delete the script after execution, if it is executed
 # between 1st Dec 2005 and 17th Dec 2005 at 4:05pm
 use Util::SelfDestruct('unlink', 
                        after => '2005-12-01',
                        before => '2005-12-17 16:05:00',


This module will prevent execution of your script by either dying or deleting (unlinking) the script from disk after it is executed. This can be useful if you have written a script for somebody that must never be executed more than once. A database upgrade script for example.

The 'self destruct' mechanism can be achieved through deleting the script so that it cannot be executed again, or by dying (terminating the scripts execution).

Die Method (default)

This is the default, and safest behaviour. This allows the script to be executed once. If it is executed again, it will immediately die during the initial compilation phase, preventing the script from fully executing.

To do this, the Util::SelfDestruct needs to know if the calling script has ever been executed before. It does this by writing a memo to a file called .selfdestruct in the user's home directory whenever the script is executed. It can therefore find out if the script has been run before during subsequent invocations.

Unlink Method

This method should be used with caution. To specify the unlink method, add the unlink boolean flag as an import paramter (see examples in the synopsis above). Aliases for the unlink flag are erase and delete.

This method will allow the script to execute, but then delete the file during the cleanup phase after execution. (Specifically during the execution of the END{} in the Util::SelfDestruct module).

Before & After Qualifiers

The default behavior of Util::SelfDestruct is to only allow a script to execute once, through either deletion of the script itself, or by dying on all subsqeuent invocations after it's first execution.

Instead of this default behaviour, the before and after options allow conditional timing of when the script will self destruct. Specifying before will cause the script to self destruct if executed before the specified date and time. Likewise, the after option will cause the script to self destruct if executed after the specified date. They can also be used in conjunction with eachother to specify a finite time frame.

Examples of valid date time formats are as follows:


Any non-numeric characters will be removed from the date time string before it is parsed. This allows more pleasing formatting to be used.

If only a date is specified and not a time, 00:00:00 is assumed in the case of the before option, and 23:59:59 is assumes in the case of the after option.


$Id:,v 1.20 2006/01/12 22:45:11 nicolaw Exp $


Nicola Worthington <>


Copyright 2005,2006 Nicola Worthington.

This software is licensed under The Apache Software License, Version 2.0.

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