What is the mean of N and M in the command "rfluka -N5 -M5 Temp.inp &"?

what is the mean of N and M in the command “rfluka -N5 -M5 Temp.inp &”?

by the way, how to use multiple cores in command line?

They respectively indicate the last completed (simulated) cycle and the last cycle to be simulated.
Anyway, these parameters are automatically set by flair and the rfluka script is automatically invoked by flair, therefore, you don’t need to touch these parameters.
You can use multiple cores using the “spawning” features. Have a look at this lecture to understand the basics of how to run a simulation: https://indico.cern.ch/event/1012211/contributions/4247768/attachments/2254501/3825143/03_Introduction_to_Flair_and_basic_input_2021_online.pdf

i know how to do in flair, but when many related simulations need to be done, for instance, a series of energic particles are used.
so sometimes, it is convinient to run fluka application in command lines,
how to use multiple cores in command line?

You can still use flair to run different primary energies using #defines: have a look at slides 22 and 23 of the flair basic lecture.
You can also do it exploiting the loop option, have a look at slide 27 of the flair intermediate lecture.
If you want to do it via command line, then you need to write you own scripts, that automatically sets the parameters you want to change of each simulation and then invokes the rfluka script.

@ amario, Thanks!