Re: _access

From:

Fenster <fenster@croctec.co.uk>

Newsgroups:

microsoft.public.vc.mfc

Date:

Mon, 31 Jul 2006 11:46:06 +0100

Message-ID:

<4REOuZCu9dzEFwEB@FensterPC.croctec.co.uk>

In message <822AAA1C-C7B5-4D9F-A36B-0E49054C84D8@microsoft.com>, Tim
<Tim@discussions.microsoft.com> writes

I2"m using _access(2ZFile.txt2\,2) to see if I have permission to write to
a file.
It works most of the time but when the file is on a network, and the network
permission for the specified user has the write permission is denied it fails.
Can anyone tell me how do I tell determine this to be true?

Thank you,
Tim

There was a thread, maybe in comp.os.ms-windows.programmer.win32, last
year about _access being broken except to confirm a file's existence. I
have a vague recollection that a Microsoft person confirmed this and
offered a non-intrusive workaround:

int CheckAccessMode(LPCTSTR pszFilename, int nMode)
{
    if (0 == nMode)
        // _access() does fine when checking for existence only
        return(_access(pszFilename, nMode));

    DWORD dwAccessMode;

    if (2 == nMode) dwAccessMode = GENERIC_WRITE;
    else if (4 == nMode) dwAccessMode = GENERIC_READ;
    else if (6 == nMode) dwAccessMode = GENERIC_READ | GENERIC_WRITE;
    else
        {
        assert(0);

        return(-1);
        }

    HANDLE hFile = CreateFile(pszFilename,
                                dwAccessMode,
                                FILE_SHARE_READ | FILE_SHARE_WRITE,
                                NULL,
                                OPEN_EXISTING,
                                FILE_ATTRIBUTE_NORMAL
                                    | FILE_FLAG_BACKUP_SEMANTICS,
                                NULL);

    if (INVALID_HANDLE_VALUE == hFile)
        return(-1);

    if (!CloseHandle(hFile))
        assert(0);

    return(0);
}

--
Fenster