&define_snapshots
filename = "gunRun.snap",
time_interval = 0.1e-9
start_time = 2e-9
&end
This command results in snapshots being taken every 100ps starting
at time 2ns, with data going to gunRun.snap.
&define_snapshots
STRING filename = NULL;
double time_interval = 0;
double start_time = 0;
&end