getting line numbers

[Thierry Horsin via ntg-context <ntg-context@ntg.nl>]

Hi everybody

Is there a way to have an automatic access to the current line number of a specific place inside a tex file ? To be more precise, here is what I would like to do.

I am currently trying to have some automatic external compilation by g++ of some portion of my tex file as in the following example below. \startC \stopC defines a framed part of text written between lines 538 and 549. Of course, if I add something before or inbetween my framed code, 538 and/or 549 will change. Thus I would like to get these two numbers automatically.

Thank you.
Thierry

\startC
#include <iostream>

using namespace std;
int mysum(int,int); int a; int b;
int main () { a=2; b=9;
  cout << mysum(a,b) << endl;
  return 0; 
        }
int mysum(int a, int b)
{ return a+b; }
\stopC

\startluacode
myout = io.open("test.cpp", "w")
myin = io.open(tex.jobname..".tex", "r")
local n=0
for line in myin:lines() do
n=n+1
if n>539 and n<550 then
    myout:write(line.."\n")
 end   
end
myout:close()
myin:close()
os.execute("g++ -o test test.cpp")
os.execute("./test > tmp")
local file=assert(io.open("tmp","r"))
local t = file:read("*all")
tex.print(t)
\stopluacode





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