It's little off-topic as there are officially no modules included in lmtx. But when I used the modules from a mkiv-installation, there was little to no problem. But with the gnuplot-module I can't fix the error myself.

MWE:

\usemodule[gnuplot]

\startGNUPLOTscript[sin]

plot sin(x)

\stopGNUPLOTscript

\starttext

\placefigure[here]{Sine Test}{\useGNUPLOTgraphic[sin]}

\stoptext

Under mkiv everything is fine. mkiv creates a file gnuplot-gnuplot-1.plt, sends this file to gnuplot and uses the output gnuplot-gnuplot-1-ctx.tex.

Under lmtx only the files gnuplot-gnuplot-1.tmp and gnuplot-gnuplot-inclusions.tmp are created. When I copy the correct .plt file from a mkiv-run, no gnuplot-gnuplot-1-ctx.tex is generated. If I copy the correct -ctx.tex file from a mkiv-run, I still get an error.

Relevant part from the logfile of a working mkiv-run:

modules > 'gnuplot' is loaded

open source > level 3, order 4, name '/home/user/context/tex/texmf-modules/tex/context/third/gnuplot/t-gnuplot.mkiv'

loading > Gnuplot module

open source > level 4, order 5, name '/home/user/context/tex/texmf-context/tex/context/fonts/mkiv/type-imp-texgyre.mkiv'

close source > level 4, order 5, name '/home/user/context/tex/texmf-context/tex/context/fonts/mkiv/type-imp-texgyre.mkiv'

close source > level 3, order 5, name '/home/user/context/tex/texmf-modules/tex/context/third/gnuplot/t-gnuplot.mkiv'

fonts > preloading latin modern fonts (second stage)

fonts > 'fallback modern-designsize rm 12pt' is loaded

open source > level 3, order 6, name 'gnuplot-gnuplot-1-ctx.tex'

close source > level 3, order 6, name 'gnuplot-gnuplot-1-ctx.tex'

metapost > initializing instance 'metafun:1' using format 'metafun' and method 'default'

metapost > loading 'metafun' as '/home/user/context/tex/texmf-context/metapost/context/base/mpiv/metafun.mpiv' using method 'default'

metapost > initializing number mode 'scaled'

floatblocks > '1' placed (here)

from a lmtx-run (no .plt-file and -ctx.tex given):

modules > 'gnuplot' is loaded

open source > level 3, order 4, name '/home/user/lmtx/tex/texmf-modules/tex/context/third/gnuplot/t-gnuplot.mkiv'

loading > Gnuplot module

open source > level 4, order 5, name '/home/user/lmtx/tex/texmf-context/tex/context/fonts/mkiv/type-imp-texgyre.mkiv'

close source > level 4, order 5, name '/home/user/lmtx/tex/texmf-context/tex/context/fonts/mkiv/type-imp-texgyre.mkiv'

close source > level 3, order 5, name '/home/user/lmtx/tex/texmf-modules/tex/context/third/gnuplot/t-gnuplot.mkiv'

fonts > preloading latin modern fonts (second stage)

fonts > 'fallback modern-designsize rm 12pt' is loaded

mtxrun |

mtxrun | executing: gnuplot gnuplot-gnuplot-1.plt

mtxrun |

/home/user/lmtx/tex/texmf-linux-64/bin/mtxrun.lua:26166: attempt to call a nil value (field 'exec')

aaa > mtxrun --direct gnuplot gnuplot-gnuplot-1.plt

floatblocks > no block given

floatblocks > '1' placed (here)

lmtx with given .plt and -ctx.tex-file:

modules > 'gnuplot' is loaded

open source > level 3, order 4, name '/home/user/lmtx/tex/texmf-modules/tex/context/third/gnuplot/t-gnuplot.mkiv'

loading > Gnuplot module

open source > level 4, order 5, name '/home/user/lmtx/tex/texmf-context/tex/context/fonts/mkiv/type-imp-texgyre.mkiv'

close source > level 4, order 5, name '/home/user/lmtx/tex/texmf-context/tex/context/fonts/mkiv/type-imp-texgyre.mkiv'

close source > level 3, order 5, name '/home/user/lmtx/tex/texmf-modules/tex/context/third/gnuplot/t-gnuplot.mkiv'

fonts > preloading latin modern fonts (second stage)

fonts > 'fallback modern-designsize rm 12pt' is loaded

mtxrun |

mtxrun | executing: gnuplot gnuplot-gnuplot-1.plt

mtxrun |

/home/user/lmtx/tex/texmf-linux-64/bin/mtxrun.lua:26166: attempt to call a nil value (field 'exec')

aaa > mtxrun --direct gnuplot gnuplot-gnuplot-1.plt

open source > level 3, order 6, name 'gnuplot-gnuplot-1-ctx.tex'

close source > level 3, order 6, name 'gnuplot-gnuplot-1-ctx.tex'

metapost > initializing instance 'metafun:1' using format 'metafun' and method 'default'

metapost > loading 'metafun' as '/home/user/lmtx/tex/texmf-context/metapost/context/base/mpiv/metafun.mpiv' using method 'default'

metapost > initializing number mode 'scaled'

floatblocks > '1' placed (here)

tex error > tex error on line 1 in file gnuplot-gnuplot-1-ctx.tex: ! Undefined control sequence

<argument> \GNUPLOTfile

-ctx.tex

\fourthoffivearguments #1#2#3#4#5->#4

<write> set output "\@@GNUPLOTresult

}\endwrite

<argument> \shipoutscratchbox

\page_shipout_box #1->\clf_shipoutpage #1

\relax \global \setbox #1\emptybox ...

...l.8 \stoptext

1 >> % Written by ConTeXt terminal for GNUPLOT on: 2019-04-10 16:12 CEST

2 % GNUPLOT version: 5.0.5, terminal version: 1.0.0 (2011-11-05)

3 % See also http://wiki.contextgarden.net/Gnuplot

4 %

5 \startGNUPLOTgraphic[1]

6 string gnuplotversion; gnuplotversion := "5.0";

7 string termversion; termversion := "1.0";

8 % scaling factor, width and height of the figure

9 a := 1cm; w := 12.700a; h := 7.620a; % (5in, 3in)

10 % temporary variable for storing the path and images

11 save p, img, ima; path p; string img, ima;

The control sequence at the end of the top line

of your error message was never \def'ed. If you have

misspelled it (e.g., `\hobx'), type `I' and the correct

spelling (e.g., `I\hbox'). Otherwise just continue,

and I'll forget about whatever was undefined.

mtx-context | fatal error: return code: 256

Sorry, can't help more, as I don't know where the problem is.

Thanks for fixing it in time, when the modules get installed with lmtx.

Christian