[vtkusers] About input file

[ldou]

I am just beginning to learn vtk,I want to know how I can
read a text input file,each line of the input file has two
formats:
species  x1 y1 z1
where species is the type of atom,like c,h,k or o,x1, y1, z1
are the coordinate of the atom in space.The other Line
format is:
-    x1 y1 z1  x2 y2 z2
where the - indicates that the line specifies the bond, the
two set of coordinates specify the start and endpoints of
the bond.