How do I set an environment variable for a Lua filter's os.execute?

[adamiturabi]

Description

I am using this Lua filter for rendering TikZ diagrams: https://github.com/danmackinlay/quarto_tikz/blob/main/_extensions/tikz/tikz.lua

On this line, it calls os.execute() to run a shell command:

local _, _, dvisvgmExitCode = os.execute("dvisvgm --font-format=woff " .. dviFile .. " -n -o " .. svgFile)

My issue is that dvisvgm needs the environment variable GSLIB set to the location of a library on my system (LIBGS=/usr/local/Cellar/ghostscript/10.04.0/lib/libgs.dylib).

How may I have this environment variable set and available to os.execute()?

Lua does not seem to have a os.setenv() function.

I've tried the following unsuccessfully:

local _, _, dvisvgmExitCode = os.execute("LIBGS=/usr/local/Cellar/ghostscript/10.04.0/lib/libgs.dylib dvisvgm --font-format=woff " .. dviFile .. " -n -o " .. svgFile)

local _, _, dvisvgmExitCode = os.execute("export LIBGS=/usr/local/Cellar/ghostscript/10.04.0/lib/libgs.dylib; dvisvgm --font-format=woff " .. dviFile .. " -n -o " .. svgFile)

local _, _, dvisvgmExitCode = os.execute("export LIBGS=/usr/local/Cellar/ghostscript/10.04.0/lib/libgs.dylib && dvisvgm --font-format=woff " .. dviFile .. " -n -o " .. svgFile)

EDIT:

I found a workaround to use the --libgs= option for dvisvgm thus:

local _, _, dvisvgmExitCode = os.execute("dvisvgm --libgs=/usr/local/Cellar/ghostscript/10.04.0/lib/libgs.dylib --font-format=woff " .. dviFile .. " -n -o " .. svgFile)

So I'm unblocked. Not sure if the original question still merits an answer.

[tarleb]

Pandoc offers the function pandoc.system.with_environment. The function doesn't seem to work reliably on Windows, but it might be good enough for many use-cases.

Usage:

pandoc.system.with_environment(
  { LIBGS = "...." },
  function ()
    os.execute('...')
  end
)

[adamiturabi]

Thank you. This worked.

But there was an issue with the filter where it was picking up an (incorrectly generated) cached version of the svg file instead of generating a new one. When I remove the cache, I notice that this solution also works:

local _, _, dvisvgmExitCode = os.execute("LIBGS=/usr/local/Cellar/ghostscript/10.04.0/lib/libgs.dylib dvisvgm --font-format=woff " .. dviFile .. " -n -o " .. svgFile)