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mksh bugfix — thank you for the music 2018-05-07 Tags: bug debian mksh pcli

I’m currently working on an mksh(1) and bc(1) script that takes a pitch standard (e.g. “A₄ = 440 Hz” or “C₄ = 256 Hz”) and a config file describing a temperament (e.g. the usual equal temperament, or Pythagorean untempered pure fifths (with the wolf), or “just” intonation, Werckmeister Ⅲ, Vallotti or Bach/Lehman 1722 (to name a few; these are all temperaments that handle enharmonics the same or, for Pythagorean in out case, ignore the fact they’re unplayable). Temperaments are rule-based, like in ttuner. Well, I’m not quite there yet, but I’m already able to display the value for MuseScore to adjust its pitch standard (it can only take A₄-based values), a frequency table, and a list and table of cent deltas (useful for using or comparing with other tuners). Of course, right now, the cent deltas are all 0 because, well, they are equal temperament against equal temperament (as baseline), but I can calculate that with arbitrary and very high precision!

For outputting, I wanted to make the tables align nicely; column(1), which I normally use, was out because it always left-aligns, so I used string padding in Korn Shell — except I’m also a Unicode BMP fan, so I had F♯ and B♭ in my table headings, which were for some reason correctly right-aligned (for when the table values were integers) but not padded right when aligning with the decimal dot. So I worked around it, but also investigated.

Turns out that the desired length was used as second snprintf(3) argument, instead of, as in the right-align case, the buffer size. This worked only until multibyte characters happened. A fun bug, which only took about three minutes to find, and is covered by a new check in the testsuite even. Thought I’d share.

Feedback on and improvements for the tuner, once it’ll be done, are, of course, also welcome. I plan to port the algorithm (once I’ve got it down in a programming language I know well) to QML for inclusion in the tuner MuseScore plugin, even. Check here, for now, for my work in progress… it’s quite big already despite doing basically nothing. Foundation laid (or so…).