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Using Shake, to create an mp3 (this is just a learning example), I use lame, and then id3v2 to tag it.

If the lame succeeds, but the id3v2 fails, then I'm left with the mp3 file in place; but of course it is "wrong". I was looking for an option to automatically delete target files if a producing command errors, but I can't find anything. I can do this manually by checking the exit code and using removeFiles, or by building in a temporary directory and moving as the last step; but this seems like a common-enough requirement (make does this by default), so I wonder if there's a function or simple technique that I'm just not seeing.

user3416536
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1 Answers1

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The reason Make does this by default is that if Make has a partial incomplete file on disk, it considers the task to have run successfully and be up to date, which breaks everything. In contrast, Shake records that a task ran successfully in a separate file (.shake.database), so it knows that your mp3 file isn't complete, and will rebuild it next time.

While Shake doesn't need you to delete the file, you might still want to so as to avoid confusing users. You can do that with actionOnException, something like:

let generateMp3 = do cmd "lame" ... ; cmd "id3v2" ...
let deleteMp3 = removeFile "foo.mp3"
actionOnException generateMp3 deleteMp3
Neil Mitchell
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