How to run a program inside LuaLaTeX?

Question

Is it possible to run a simple script inside LuaLaTeX or LaTeX?

For example, I need to use the calculator from the terminal. I'd like to write

$echo "100.83*4.53" | bc

and obtain the result in LuaLaTeX or LaTeX. Is there a command (called \runscript, for instance) that runs a script from within LuaLaTeX or LaTeX and that I could use as follows:

\runscript{echo "100.83*4.53" | bc}

and get "456.7599" as result?

Is it possible, perhaps with some Perl or Python script?

Answer 1

With LuaTeX you can do something like this:

\documentclass{article}
\usepackage{luacode}
\begin{document}

\def\foo{\directlua{dofile("runfunc.lua")}}
\foo
\end{document}

and the file runfunc.lua is this:

local i,j = io.popen([[echo "100.83*4.53" | bc]])
if not i then
  print(j)
  os.exit(-1)
end
tex.sprint(-2,string.gsub(i:read("*all"),"%s*$",""))
i:close()

run with

lualatex --shell-escape ‹filename.tex›

to allow io.popen().