#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>

#define CHECK(cond) if( !(cond) ) { printf("%s failed at %s:%d\n", #cond, __FILE__, __LINE__); exit(1); }

const char *fname = "//s-cw-head/pgas/test.bin"; // Works with simple "c:/test.bin"

int main() {
  // Without this snippet everything works
  int perm = S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH;
  int mode = O_WRONLY | O_CREAT | O_TRUNC;
  int fd = open(fname, mode, perm);
  CHECK( -1 != fd );
  close(fd);

  // Main part

  FILE *p = fopen(fname, "rb+");
  CHECK(p);

  long long data = -1;
  CHECK( sizeof(data) == fwrite(&data, 1, sizeof(data), p) );

  CHECK( 0 == fseek(p, 0, SEEK_END) );
  CHECK( ftell(p) == sizeof(data) );

  printf("success\n");

  return 0;
}