Microsoft KB Archive/105763

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HOWTO: Use NTFS Alternate Data Streams

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Q105763

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The information in this article applies to:


 * Microsoft Win32 Application Programming Interface (API), used with:
 * the operating system: Microsoft Windows NT, versions 3.1, 3.5, 3.51, 4.0
 * the operating system: Microsoft Windows 2000

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SUMMARY
The documentation for the NTFS file system states that NTFS supports multiple streams of data; however, the documentation does not address the syntax for the streams themselves.

The Windows NT Resource Kit documents the stream syntax as follows:

"filename:stream" Alternate data streams are strictly a feature of the NTFS file system and may not be supported in future file systems. However, NTFS will be supported in future versions of Windows NT.

Future file systems will support a model based on OLE 2.0 structured storage (IStream and IStorage). By using OLE 2.0, an application can support multiple streams on any file system and all supported operating systems (Windows, Macintosh, Windows NT, and Win32s), not just Windows NT.

MORE INFORMATION
The following sample code demonstrates NTFS streams:

Sample Code
  #include    #include 

void main {     HANDLE hFile, hStream; DWORD dwRet;

hFile = CreateFile( "testfile",                      GENERIC_WRITE,                    FILE_SHARE_WRITE,                                NULL,                         OPEN_ALWAYS,                                   0,                                NULL ); if( hFile == INVALID_HANDLE_VALUE ) printf( "Cannot open testfile\n" ); else WriteFile( hFile, "This is testfile", 16, &dwRet, NULL );

hStream = CreateFile( "testfile:stream",                               GENERIC_WRITE,                             FILE_SHARE_WRITE,                                         NULL,                                  OPEN_ALWAYS,                                            0,                                         NULL ); if( hStream == INVALID_HANDLE_VALUE ) printf( "Cannot open testfile:stream\n" ); else WriteFile(hStream, "This is testfile:stream", 23, &dwRet, NULL); } The file size obtained in a directory listing is 16, because you are looking only at "testfile", and therefore

"type testfile" produces the following:

  This is testfile However

"type testfile:stream" produces the following:

  The filename syntax is incorrect In order to view what is in testfile:stream, use:

"more < testfile:stream" "-or-" "mep testfile:stream" where "mep" is the Microsoft Editor available in the Platform SDK.

Additional query words:

Keywords : kbAPI kbFileIO kbKernBase kbOSWin2000 kbDSupport kbGrpDSKernBase

Issue type : kbhowto

Technology : kbAudDeveloper kbWin32sSearch kbWin32API