Greetings,
I am trying to run one of GEANT4 extended examples, which is FissionFragment. However, it is asking me to set an environment before running. I do not know how to do that honestly. Here is a capture:
How to set the environment above? Sorry it might seem very easy but I am a new user.
Figured it out. It was so simple: export G4NEU…=“geant4 location/data”
How did you export those variable?
I can’t find G4NEU… at my geant4_location/data.
Should I make it? Or download some other thing?
Look at the name string quoted in the screenshot originally posted. The author wrote “G4NEU…” as an abbreviation for “G4NEUTRONHP_PRODUCE_FISSION_FRAGMENTS”.
Oh, I knew that G4NEU… is an abbreviation for G4NEUTRONHP_PRODUCE_FISSION_FRAGMENTS.
What I meant was I can’t find the “G4NEUTRONHP_PRODUCE_FISSION_FRAGMENTS” at my geant4_location/data.
Anyway, thank you for your reply! 
That’s not going to be the name of the file. It’s the name of the envvar. Looking into the code (G4ParticleHPManager.cc) it looks like it does not need to have a value at all, it just has to exist:
if ( getenv( "G4NEUTRONHP_PRODUCE_FISSION_FRAGMENTS" ) ) PRODUCE_FISSION_FRAGMENTS = true;
So you should be able to set
export G4NEUTRONHP_PRODUCE_FISSION_FRAGMENTS=yes
and get the fragments produced as secondaries.
Thank you for your reply, mkelsey. It was really helpfull!
in examples/extended/hadronic/Hadr03 you will find envHadronic.sh (or csh) which illustrates how to set such environment variables.
Thank you for your specific comment maire.