@User Xschem has a set of command line options that allow xschem to be used in batch environment, for example, given a finished schematic --> produce a spice netlist --> run ngspice sim. All this can be run as a command, like:

xschem -x -s -n -S -q ./sky130_tests/test_inv.sch

where:

-x : don't use graphics at all (faster startup)

-s : set netlist mode to spice

-n : generate netlist of given schematic

-S : run ngspice on netlist

-q : quit after processing commands.

If you have specific issues on xschem side feel free to ask (here or if very xschem related in #xschem channel)