[Haskell-beginners] a way to check whether a file is actually being written on

[Silent Leaf]

strace sounds really great, i'll test it, thanks :)

2017-06-27 22:42 GMT+02:00 Jona Ekenberg <saikyun at gmail.com>:

>
>
> Den 27 juni 2017 9:47 em skrev "Silent Leaf" <silent.leaf0 at gmail.com>:
>
> Hi,
>
> i created a small clone of dd in haskell. I made it so it only copies
> block by block and only if there's any difference between each pair of
> blocks from each file. the idea is to use this dd clone as backup system,
> especially since my partitions are nearly full, so no real loss in copying
> the whole things.
>
> I'm wondering if there's any way to check if my program never ever writes
> onto the target unless actually needed. obviously by reading the code i'd
> say it does what i want, but we do make test cases rather than rely on what
> we think the code does.
>
> i can't run it with a target file that would be made read-only in the
> filesys (and hope for an error for trying to write on it) since obviously i
> need to open it in read-write right from the beginning, in case of actual
> need of writing (as apparently i can't have two handles on the same file...
> although maybe there's a way to change the mode of opening on the run? did
> not find it in System.IO nor in Hoogle or Hayoo)
>
> so if anyone has an idea, in or outside of haskell, that would be great!
> ______________________________
>
> Maybe you can use strace? https://youtu.be/4pEHfGKB-OE
>
>
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