Src for a pair of win32 console programs to demonstrate cross-process file access.

SharedFileClient.cpp

// SharedFileClient.cpp : Defines the entry point for the console application.
//

#include "stdafx.h" 
#include <windows.h> 
#include <time.h>

void EmitError(DWORD dwErr) 
{
	if(dwErr != 0) 
	{
		LPVOID tszBuf = 0;
		DWORD dwFmt = FormatMessage(
			FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM,
			0, dwErr, 0, (LPTSTR)(&tszBuf), 0, 0);
		_tprintf(_T("Message:\r\n--\r\n%s\t\n"), (LPTSTR)tszBuf); 
		if(tszBuf){::LocalFree(&tszBuf);} 
	}
}

int _tmain(int argc, _TCHAR* argv[]) 
{
	_tprintf(_T("** Begin Main Thread\r\n")); 
	_tprintf(_T("Creating File\r\n")); 
	HANDLE hFile = ::CreateFile(_T("C:\\data\\tmp\\sharetest.txt"), 
		(GENERIC_READ | GENERIC_WRITE), 
		(FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE),
		0, OPEN_EXISTING, 
		FILE_ATTRIBUTE_NORMAL | FILE_ATTRIBUTE_TEMPORARY | FILE_FLAG_DELETE_ON_CLOSE, 
		0);

	DWORD dwErr = GetLastError();
	if(dwErr != 0) 
	{
		EmitError(dwErr);
		_tprintf(_T("** Exit Main Thread\r\n")); 
		Sleep(60000);
		return 1; 
	}

	time_t ttStart = time(0);
	time_t ttCurrent = 0;
	time_t ttLast = 0;

	do
	{
		ttCurrent = time(0);
		if(ttCurrent != ttLast)
		{
			::SetFilePointer(hFile, 0, 0, FILE_BEGIN);
			DWORD dwData = 0;
			DWORD dwIn = 0;
			if(::ReadFile(hFile, &dwData, sizeof(DWORD), &dwIn, 0) == TRUE)
			{
				_tprintf(_T("Read %d bytes. [0x%8.8x]\r\n"), dwIn, dwData);
			}
			else
			{
				EmitError(GetLastError());
			}
			ttLast = ttCurrent;
		}

		Sleep(500);
	}
	while(ttCurrent < (ttStart + 30));

	::CloseHandle(hFile);

	_tprintf(_T("** End Main Thread\r\n")); 
	Sleep(60000);

	return 0; 
}

SharedFileHost.cpp

// SharedFileHost.cpp : Defines the entry point for the console application.
//

#include "stdafx.h" 
#include <windows.h> 
#include <time.h>

void EmitError(DWORD dwErr) 
{
	if(dwErr != 0) 
	{
		LPVOID tszBuf = 0;
		DWORD dwFmt = FormatMessage(
			FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM,
			0, dwErr, 0, (LPTSTR)(&tszBuf), 0, 0);
		_tprintf(_T("Message:\r\n--\r\n%s\t\n"), (LPTSTR)tszBuf); 
		if(tszBuf){::LocalFree(&tszBuf);} 
	}
}

int _tmain(int argc, _TCHAR* argv[]) 
{
	_tprintf(_T("** Begin Main Thread\r\n")); 
	_tprintf(_T("Creating File\r\n")); 
	HANDLE hFile = ::CreateFile(_T("C:\\data\\tmp\\sharetest.txt"), 
		(GENERIC_READ | GENERIC_WRITE), 
		(FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE),
		0, CREATE_ALWAYS, 
		FILE_ATTRIBUTE_NORMAL | FILE_ATTRIBUTE_TEMPORARY | FILE_FLAG_DELETE_ON_CLOSE, 
		0);

	DWORD dwErr = GetLastError();
	if(dwErr != 0) 
	{
		EmitError(dwErr);
		_tprintf(_T("** Exit Main Thread\r\n")); 
		Sleep(60000);
		return 1; 
	}

	time_t ttStart = time(0);
	time_t ttCurrent = 0;
	time_t ttLast = 0;

	do
	{
		ttCurrent = time(0);
		if(ttCurrent != ttLast)
		{
			::SetFilePointer(hFile, 0, 0, FILE_BEGIN);
			DWORD dwData = (DWORD)(ttCurrent & 0xFFFFFFFF);
			DWORD dwOut = 0;
			if(::WriteFile(hFile, &dwData, sizeof(DWORD), &dwOut, 0) == TRUE)
			{
				_tprintf(_T("Wrote %d bytes. [0x%8.8x]\r\n"), dwOut, dwData);
			}
			else
			{
				EmitError(GetLastError());
			}
			ttLast = ttCurrent;
		}

		Sleep(500);
	}
	while(ttCurrent < (ttStart + 60));

	::CloseHandle(hFile);

	_tprintf(_T("** End Main Thread\r\n")); 
	Sleep(60000);

	return 0; 
}