How overwrite file in next timestep.

Question

HI. I have this code on c++.

File file("poisson.vtu");
while (t <= te) 
{
  solve(a==L, u, bcs); 
  file << u;
  u0 = u;
  t = t + dt;  
}

In each iteration fenics create new file poisson_p0_000000.vtu, poisson_p0_000001.vtu and etc. How i can overwrite poisson_p0_000000.vtu in each step and don't create new files?

Answer 1

What about

while (t <= te) 
{
  solve(a==L, u, bcs); 
  File file("poisson.vtu");
  file << u;
  u0 = u;
  t = t + dt;  
}

Answer 2

As Jan pointed out below, if you instantiate the File object within the loop it will overwrite the file rather than write a new file with an index to it. At the end of the while block the instance will dispose so you can create another.

// File file("poisson.vtu");
while (t <= te) 
{
  solve(a==L, u, bcs); 

  // fresh instance of file
  File file("poisson.vtu");

  file << u;
  u0 = u;
  t = t + dt;  
}