[texhax] \write18 syntax

[Joel C. Salomon]

I'm trying to typeset the documentation for unicode-math, and the .dtx
includes commands like

% \immediate\write18{xelatex -interaction=batchmode
-jobname=unicode-math-testbf-tex
"""\noexpand\PassOptionsToPackage{math-style=TeX}{unicode-math}\noexpand\input
unicode-math-testbf.ltx"""}

I'm not sure why, but these aren't working.  The log confirms that
\write18 is enabled, but there's no reference to these jobs being run.

Anyway, I figure I'll just run the command myself at the cmd.exe prompt
-- but what is the command to run?

Thanks,
--Joel