[Gmsh] obtaining numbers of geometric sub-elements

[Manav Bhatia]

Hi

Given a volume and its identification, is there a way to find out the  
identification numbers of the surfaces that make up the volume?  
Similarly, can the line numbers for a surface be found out?

Also, I am unable to locate the fault in this statement

tmp[] = Extrude Line {1, {1,0,0}};

where Line 1 already exists, and I am trying to get the number of  
surface created as a result of this operation.

Thanks
Manav