Make prints of mpiexec arguments rather than the arguments of the program being executed

Question

Why does the following code, compiled with mpicc and executed with mpiexec -n 4 prg prints prg and not mpiexec. How can I make my program print mpiexec ?

#include <stdio.h>
#include <mpi.h>
int main(int argc, char *argv[])
{
  printf("Command executed : %s\n",argv[0]);
  MPI_Init(NULL, NULL);
  /* some code */
  MPI_Finalize();
}

Answer 1

It is impossible to tell how your binary was called (in a general, portable way). MPI offers no way to determine that. Even mpiexec itself is only loosely specified.

It's generally impossible even without MPI and multiple systems being involved. prg could have been called in any number of ways such as:

/bin/env prg
bash -c 'prg'
./my_prg_wrapper.sh
x='() { :;}; prg'