[Gmsh] How to have unknown number of lines in a given surface

[saber EL AREM]

Hi,I am trying to built a 2D mesh: It is a (big)  plane surface (let's say {1})  containning a random number of smaller surfaces. 
For all the inner lines, I need to do  : 
Line {line_numer } In Surface {1}but I don't know the lines numbers, and would like to do this operation using a loop for a faster meshing procedure. 
Any idea ?
Regards,
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