[c++] check if a process is already running

Maybe it's a very simple question and linux had a nice API for it, but i cannot find it.

I am making an aplication that ensures that 1 instande of the application hcidump is running.
So i want something like:

Code:

---

if(!hcidump.IsActive())
{
  system("hcidump -w somefile &");
}

---

but how do I check if hcidump is already activated?