[metapost] feature request: quiet mode / creation date

[Reinhard Kotucha]

On 2017-07-20 at 16:19:42 +0200, Niklas Beisert wrote:

 > a) The generated figure files contain a timestamp of the creation date:
 >  %%CreationDate: 2017.07.17:1654
 > I'm not sure what the actual benefit of this timestamp is besides
 > bookkeeping. However, one drawback is that the file CHANGES each time
 > mpost is run even though the content may not have changed. If metapost
 > is run automatically each time the latex document is compiled, this may
 > result in a great number of individual files being changed. Not a major
 > issue, but it becomes a bit of a hassle if the output files are being
 > synchronised or versioned. A simple solution would be a new command line
 > option to suppress this line (and ideally also the timestamp given in
 > the first line of .log files). As far as I can see, the output files
 > without such a timestamp would be stable, i.e. they change only if the
 > contained graphics changes.

Hi Niklas,
the problem is that all MetaPost files are compliled regardless
whether their source code had been changed.  I know that TeX's
interface to the underlying operating system is quite poor and that
it's almost impossible to compare filesystem time stamps in a portable
way.

But there is texlua.  Instead of invoking mpost on every MetaPost
source file, you can as well invoke a texlua script which runs mpost
only if the .mp file is newer than the corresponding .mps file.

texlua allows you to write scripts which are completely
platform-independent.  Comparing filesystem time stamps is possible.

If you are not not familiar with Lua yet, let me know.  I could
provide such a script at the upcoming weekend.  Programming in Lua is
a pleasure.

It seems wrong to me to suppress time stamps in generated files.  It's
more approppriate not to generate them at all unless the source code
was changed.

Regards,
  Reinhard

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Reinhard Kotucha                            Phone: +49-511-3373112
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