Is it possible to derive the absolute numerical value of lambda(λ) from the mosfet model files ? Could anyone show how to do so ?
Do you mean: run a simulation of a mosfet using the model file and from the results, calculate lambda? Yes you can get an approximation at an operating point. Not sure that is what you are asking, however. If not, ask again in a different way.
BTW, unless it is a homework problem, trying to get the "exact" value of lambda (CLM parameter) is a useless exercise.
Alternatively, could I just use https://github.com/imr/ngspice/blob/master/examples/xspice/table/modelcards/modelcard.nmos#L38 directly ?
The lambda in that model is NOT the "channel length modulation" parameter.
Besides, what does TOXE = 1.8E-009 actually give ? 1.8*10^(-9) ? I asked this because I saw LC = 5E-9 in the same file
yes, 1.8E-009 is 1.8*10^(-9)