What does it mean to run a .ltb file through LaTeX?

Question

The AMSRefs package documentation says the following in Section 2.2 Using an .ltb database file:

[S]uppose you have a file nonsense.ltb with the following contents:

\documentclass{article}

\usepackage{amsrefs}

\begin{document}

\begin{bibdiv}

\begin{biblist}

\bib{Bourbaki70}{book}{
    title={Th\’eorie des ensembles},
    author={Bourbaki, Nicolas},
    date={1970},
    publisher={Hermann},
    address={Paris}
}

\bib{Sokal96}{article}{
    title={Trangressing the boundaries},
    subtitle={Toward a transformative hermeneutics of quantum gravity},
    author={Sokal, Alan},
    journal={Social Text},
    volume={46/47},
    date={1996},
    pages={217--252}
}

\bib{SokalB1998}{book}{
    title={Fashionable Nonsense},
    subtitle={Postmodern Intellectuals’ Abuse of Science},
    author={Sokal, Alan},
    author={Bricmont, Jean},
    publisher={Picador USA},
    address={New York},
    date={1998}
}

\end{biblist}

\end{bibdiv}

\end{document}

Before seeing how this affects our sample document, take note of a couple of aspects of the format of nonsense.ltb:

1. We have chosen to format nonsense.ltb as a complete LaTeX document. This is so we can produce a formatted listing of our whole database by running nonsense.ltb through LaTeX. However, this is not necessary; when amsrefs treats nonsense.ltb as a database file, it ignores everything except for the \bib commands.

   …

What is meant by "running nonsense.ltb through LaTeX"? Do I open the database file nonsense.ltb in my LaTeX editor (I am using TeXShop) and then run pdftex? But won't this require it to be a .tex file, rather than an .ltb file?

I actually tried creating a file nonsense.ltb with the above content and opening it in TeXShop, but the options to typeset the document as either 'Plain TeX' or 'LaTeX', etc. under the Typeset menu bar item are grayed out, and I'm unable to typeset the .ltb file. These are the options I see when I open in the menu bar in this case:

This is how the menu bar item looks for other (.tex) documents that I am able to typeset using ⌘T.

Answer 1

TeXShop is trying to be (not) very smart and it only allows files with extensions .tex and, as far as I can see, also .ltx to be typeset.

However, you can act on a hidden preference. On a Terminal window, type

defaults write TeXShop OtherTeXExtensions \(ltb\)

and hit return. Thereafter you will be able to typeset also .ltb files.

As you see, the “Typeset” button is no longer grayed out. Here's the console output:

The resulting PDF is:

Alas, the hidden preference is not even listed in the documentation coming with the program.

The value of the preference must be a comma separated list in parentheses, so you could do

defaults write TeXShop OtherTeXExtensions \(ltb,abc,def\)

if you need to add other extensions.