#include <errno.h>
#include <string.h>
#include <unistd.h>

int getlogin_r(char* name, size_t size) {
  char* logname = getlogin();
  if (!logname)
    return ENXIO; /* or...? */
  if (strlen(logname) >= size)
    return ERANGE;
  strcpy(name, logname);
  return 0;
}