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Opening Files

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The new home for Visual Studio documentation is Visual Studio 2017 Documentation on docs.microsoft.com.

The latest version of this topic can be found at Opening Files.

In MFC, the most common way to open a file is a two-stage process.

To open a file

  1. Create the file object without specifying a path or permission flags.

    You usually create a file object by declaring a CFile variable on the stack frame.

  2. Call the Open member function for the file object, supplying a path and permission flags.

    The return value for Open will be nonzero if the file was opened successfully or 0 if the specified file could not be opened. The Open member function is prototyped as follows:

    virtual BOOL Open( LPCTSTR lpszFileName, UINT nOpenFlags, CFileException* pError = NULL );

    The open flags specify which permissions, such as read-only, you want for the file. The possible flag values are defined as enumerated constants within the CFile class, so they are qualified with "CFile::" as in CFile::modeRead. Use the CFile::modeCreate flag if you want to create the file.

The following example shows how to create a new file with read/write permission (replacing any previous file with the same path):

         TCHAR* pszFileName = _T("c:\\test\\myfile.dat");
         CFile myFile;
         CFileException fileException;

         if ( !myFile.Open( pszFileName, CFile::modeCreate |   
                 CFile::modeReadWrite, &fileException ) )
         {
            TRACE( _T("Can't open file %s, error = %u\n"),
               pszFileName, fileException.m_cause );
         }

Note

This example creates and opens a file. If there are problems, the Open call can return a CFileException object in its last parameter, as shown here. The TRACE macro prints both the file name and a code indicating the reason for failure. You can call the AfxThrowFileException function if you require more detailed error reporting.

See Also

CFile Class
CFile::Open
Files