Re^2: Perl Best Practices book: is this one a best practice or a dodgy practice?

[TheDamian]

The problem in this case is not really about whether the program is re-runnable, but about the fact that it corrupts your data.

Neither of which is what the original recommendation is about. That recommendation, as it appears in "Perl Best Practices" is:

In-situ Arguments

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Allow the same filename to be specified for both input and output.

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And that most definitely is a best practice.

The issue raised here is that one of the two solutions suggested in the book is apparently more limited in applicability than I indicate in the text (a deficiency I have already mentioned that I'll be remedying as soon as I can).

Now it may well be that "Perl Best Practices" would benefit from the addition of an extra guideline; one that suggests using a transactional approach to avoid corrupting data. But that's only peripherally related to this guideline. It should definitely be a separate suggestion, since the problem of data corruption is not unique to opening the same file twice.

[mikeraz]

My copy is at home, as is my co-worker's copy. Hopefully I'm not saying something fundamentally stupid here.

Perhaps the solution to this entire muddle is to have as the first line of commentary after that best practice read:
Allowing the same name ensures your program will operate correctly when users, inevitably, do specify the same filename. Be Prepared, as the teach Boy Scouts 1.


1 If you have trouble remembering the Scout's famous motto, seek out the Tom Lehrer recording and have that song play through your head while coding.