CreateFile Fails - Second Execution On Same File

[Le Chaud Lapin]

Hi All,

See code below. Why does the second call fail?

Do I misunderstand the MSDN documentation?

http://msdn.microsoft.com/en-us/library/aa363858(VS.85).aspx

TIA,

-Le Chaud Lapin-

#include <windows.h>

int main (int argc, char *argv[], char *envp[])
{
// Please make sure the following file exists before running:
TCHAR szFilePath[] = "C:\\FOO.DOCX";

HANDLE h1 = CreateFile (
szFilePath,
GENERIC_READ | GENERIC_WRITE,
FILE_SHARE_READ | FILE_SHARE_WRITE,
NULL,
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL,
NULL);

HANDLE h2 = CreateFile (
szFilePath,
GENERIC_READ,
FILE_SHARE_READ,
NULL,
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL,
NULL);

DWORD dwError = GetLastError();

return 0;
}

[Uwe Sieber]

Because it's opened for writing and the second
call don't want to share write. With
"FILE_SHARE_READ | FILE_SHARE_WRITE" it will
work.

Uwe

[David Lowndes]

>See code below. Why does the second call fail?

Because the first instance is opened for reading and writing, the
second one needs to allow the same sharing. i.e. it should be:

HANDLE h2 = CreateFile (
szFilePath,
GENERIC_READ,
FILE_SHARE_READ | FILE_SHARE_WRITE,
NULL,
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL,
NULL);

You can test these usages of CreateFile using multiple instances of my
CFTest utility:
http://jddesign.co.uk/products/freeware/freeware_programs.htm#CFTest

Dave

[Uwe Sieber]

David Lowndes wrote:
>
> You can test these usages of CreateFile using multiple instances of my
> CFTest utility:
> http://jddesign.co.uk/products/freeware/freeware_programs.htm#CFTest

Here is mine :-)
http://www.uwe-sieber.de/files/CreateFileTest.zip

Uwe