Practical determination of fopen() concurrency

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main()
{
  int i;

  for(i = 1; i != 10000; ++i)
  {
    char  filename[101];
    int   n = sprintf(&filename[0], "file-%d", i);
    FILE* stm = fopen(filename, "w");

    if(NULL == stm)
    {
      fprintf(stderr, "failed to create %s: %s; FOPEN_MAX=%d\n", filename, strerror(errno), FOPEN_MAX);

      return EXIT_FAILURE;
    }
  }

  return EXIT_SUCCESS;
}