[Scilab-Dev] save(..) with internal timestamp? MD5 varying with unchanged content to be saved.

[Serge Steer]

A simple solution could be to save the date together with f
dt=datenum()
save test.sod datenum f


then
load test.sod datenum

Serge
Le 10/06/2015 00:03, Samuel Gougeon a écrit :
> Hi,
>
> I have N figures. I would like to re-export only those that were
> modified in the meanwhile.
> Indeed, exporting with xs2### is rather time-consuming, in such a way
> that i am looking for a short-circuit.
>
> The way that i imagined is the following, for a figure of handle f :
> 1) f is saved in file1.sod. This is quite faster than exporting.
> 2) later, f is re-saved in file2.sod
> 3) we compute the MD5 checksums of the contents of file1.sod and file2.sod
> 4) we compare both checksums. If they are different, we re-export f.
>
> Unfortunately, it looks that save(..) likely saves also an internal
> timestamp, or something varying external to the main saved content.
> This ruins the idea, and i do not see any reflief plan. Here is a proof:
> clf
> plot2d()
> f = gcf();
> save test.sod f
> getmd5 test.sod
> sleep(5000)
> save test.sod f
> getmd5 test.sod  
> Yielding:
>
> -->clf
> -->plot2d()
> -->f = gcf();
> -->save test.sod f
> -->getmd5 test.sod
>  ans  =
>  e015481486eb9708a4fe1d3df1cbbbb9  
> -->sleep(5000)
> -->save test.sod f
> -->getmd5 test.sod
>  ans  =
>  3c6319b5d3a2299caaacc2f95c3efb32  
>
> Other tests show that
> 1) renaming the file does not change its checksum returned by getmd5()
> 2) modifying the OS timestamp of the file (any of creation, last
> access, last write) does not change its checksum.
>
> Hence, it really looks that an internal timestamp is recorded with the
> proper data.
> So, my questions are :
> 1) do -- you developers -- confirm this save()'s behavior? I did you
> go the the source code.
> 2) Why doing that? Is is on purpose, or is it a bug?
> 3) Is there a way to avoid it?
>     a) There is presently no usage option to avoid it
>     b) On option, recording only the date with a fixed conventionnal
> hour such that 00:00:00.000 would be ok for me.
>         10s of export is <<< 24h ;)
> 4) Would you have any idea to do what i expect with figures, without
> using their saved handles?
>     I posted a wish and proposal
> http://bugzilla.scilab.org/show_bug.cgi?id=11658  3 years ago, in
> order to
>     open the possibillity to save copies of handles (in structures)
> and then becomes able to compare them.
>     But the thread does not breathe...
>
> Reading you soon
>
> Samuel
>
>
>
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