In the first part of this post we very briefly looked at what happens when you grab the raw luatex.exe binary and run it: in short, not a lot!

Of environment variables and search paths

In today’s era of graphical user interfaces: Windows, Mac OS X, Gnome, KDE and so forth, the experience of software installation, especially on Windows and Mac, is typically a point-and-click affair. Not a command line in sight. For those who are taking their first steps into the TeX world, it can, depending on your setup, be a very new experience. During the course of these tutorials, which focus on a do-it-yourself LuaTeX install, the DOS prompt and command line will become your closest allies. When writing this sort of tutorial it is always difficult to balance the desire to be thorough without boring more experienced readers with detail they find too trivial. I’ll do my best to get it right but I’ll assume very little apart from feeling comfortable with a command-line world.

Telling LuaTeX about its environment

One of the first things you need to realise is that LuaTeX needs to know something about the “computer environment” in which it is running; you need to provide it with some fundamental information so that it is able to locate the resources it needs to do its job of typesetting. This help or guidance for LuaTeX is provided through a mechanism called environment variables. In essence, environment variables are used to store values which a program can access when it is running. Windows predefines a number of standard “system environment variables”, such as PATH, but you are free to add new ones according to the needs or requirements of the different programs you use. For LuaTeX, there are a number of very important environment variables you need to set before it can find anything, such as fonts, .tex files, graphics, encoding vectors etc, on your computer.

Web2C and Kpathsea: a primer
If you want to skip past my explanations and plunge straight into the detail then head on over to http://www.tug.org/texinfohtml/kpathsea.html. A great resource which provides interesting historical background by Karl Berry.

LuaTeX environment variables

Firstly, I should say that I’m using the term “LuaTeX environment variables” which may imply that any environment variables I mention are specific to LuaTeX: generally, they are not, so please forgive this slight simplification in the interest of clarity. Occasionally there may be an environment variable which is specfic to LuaTeX and where that is the case I’ll try to point it out. In the next installment I’ll zoom in on texmf.cnf, your passport to the joys of a minimal LuaTeX installation.