Command line option -e?

[Rick Hansen (aka RickH)]

Is there a way that I can assign a value to a variable in the lilypond
command line, then make that variable available to my lilypond code?  Using
the -e option?

I maintain my songs in separate scores then I compile them to PDF, when I'm
assembling my final "book" I use ghost writer to concatenate the PDF's (some
of the PDF's might be Word documents, lilypond, web page conversions to PDF,
whatever) into the final book.

So when I'm compiling my lilypond PDF I'd like to be able to pass into my
template a variable that contains the appropriate starting page number and
also another variable that might contain different heading text.

Reading the manual it seems like I should be able to do this, but so far no
luck and I could not find an example.  Ideally here is what I'd like the
command line to do:

lilypond -e '(myStartingPage = 24)' -e '(myHeading = "Example 3")' mySong.ly

Then in my code I would be free to use the variables called "myStartingPage"
and "myHeading" in any way I want.

Basically I want to input variables through the command line for things that
are totally dependant on usage rather than on something permanent where I
would want to re-edit the source code.  "Purpose based" compiling for lack
of a better word.



Would a better alternative be to use the "--include" option and put all my
job-specific variables into a file called "job.ly" in separate folders by
job, then simply change the search path depending upon what job I'm running
to pull in a different "set" of variables?  This way if I'm compiling for
the purpose of inclusion in a book as opposed to stand-alone I can have 2
different "job.ly" files in separate folders?  Where job.ly is
unconditionally \include at the top of my template?

Now that I think of it, this might be cleaner to just run with a different
--include path.  Can this be done?  Would this technique be better for
language localization of my scores also, by defining my language-sensitive
content in a separate "bylanguage.ly" file and using "--include" to point at
the Spanish path as opposed to the English path?


Can someone please give me some opinions on best practice for implementing
job-specific runs of a single lily file?  I apologize if this is already in
the manual and I missed it.



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