Re: reading string from a text file from vc++ without MFC support

Sat, 16 Jun 2007 23:11:11 -0700
On Jun 16, 12:01 pm, MrAsm <> wrote:

On Fri, 15 Jun 2007 22:28:32 -0700, wrote:

need need to again read is y code which is working fine
for writing tofile:
           fp=_wfopen(lstr,_T("w+"));//lstr is having the path to thefile
           fwrite( strTitleCurrentDate, sizeof(TCHAR), strTitle.GetLength()/
** sizeof( TCHAR )*/, fp );
           fclose( fp );
this code is working fine but

The previous code is not good.

You are using _T and Unicode (_wfopen) in a wrong way.
_wfopen is the Unicode version of fopen, its prototype is:

    const wchar_t *filename,
    const wchar_t *mode

So 'mode' is a Unicodestring(wchar_t *) in _wfopen, so you should
use L"w+", not _T("w+"), with _wfopen.

Or, if you want to use Unicode-aware style consistently, you can

  // Assume 'lstr' is a TCHAR-string(e.g. a CString)
 FILE* fp = _tfopen( lstr, _T("w+") );

Your original code would compile only in Unicode builds, but is
inconsistent with TCHAR convention.

Moreover, the fwrite line does not very much make sense:

           fwrite( strTitleCurrentDate, sizeof(TCHAR), strTitle.GetLength()/
** sizeof( TCHAR )*/, fp );

You are writing 'strTitleCurrentData' characters, but you are giving
fwrite the length of 'strTitle'... are these variables the *same*string? If so, why are you using two different variables for the samestring? The code is confusing...

Moreover, if 'strTitleCurrentDate' is of type CString, I would prefer
to explicitly cast to LPCTSTR to accessstringcharacter pointer.

Finally, are you aware that you are writing only thestringcharacters
but *no* the final _T('\0') of thestring? In fact, GetLength returns
the number of TCHARs in thestring, excluding the terminating

   CString strTitle1;
sizeof( TCHAR ));

'strTitle1' is initialized to an emptystringby the default
constructor. So 'strTitle1.GetLength()' is 0, so you are passing 0 to
Is that what you really want??

LPTSTR lstr=strPath2.GetBuffer(strTitle.GetLength()* sizeof( TCHAR ));

You have the same Unicode/_T (_wfopen/_T("a+")) mismatch as above.

   fread( newBuffer, sizeof(char), 100/** sizeof( TCHAR )*/, fp );
fclose( fp );

You called GetBuffer above, but you didn't release the buffer with
Moreover, where is the 'newBuffer' memory?
Where is defined that 'newBuffer' is 100 bytes?
Why are you using 'char' and not 'TCHAR'?

IMHO, the code has several inconsistent things...
You should really clean it up.

You might consider using more modern C++ I/O stream classes to manage
files; they are easier than CFILE*, are more robust (e.g. the
destructor will close thefile, while with CFILE* you may forget to
call fclose, etc.)

If you want to write to afile, you may use code as follow:

  // Yourfileobject
  std::ofstreamfile( "TheFileName.txt" );

  // You may check result withfile.is_open()
  // if (file.is_open() ...

  // Write tofile:
 file<< "This is the first line.\n";
 file<< "Hello...\n";
  ... and so on

  // You may callfile.close() or let the
  // class destructor close thefilewhen
  // 'file' variable goes out of scope.

If you want to read from afile, line by line:

  // if (!file.is_open()) --> error

  // Linereadingloop
  while ( !file.feof() )
    std::getline(file, line );
    std::cout << "Line read: " << line << std::endl;

  //file.close() or delegate to destructor

There is also the MFC CStdioFile class, but I would prefer a
substitute from CodeProject (or Tom's much better version):


Thanks a lot MrAsm for your precious suggestions,I have made the
changes in the code to what you suggested(such as _wfopen to
_tfopen,charto TCHAR etc.).But the code what you have sent {

If you want to write to a file, you may use code as follow:

  // Your file object
  std::ofstream file( "TheFileName.txt" );

  // You may check result with file.is_open()
  // if ( file.is_open() ...

  // Write to file:
  file << "This is the first line.\n";
  file << "Hello...\n";
  ... and so on

  // You may call file.close() or let the
  // class destructor close the file when
  // 'file' variable goes out of scope.

If you want to read from a file, line by line:

  std::string line;
  std::ifstream file("Data.txt");
  // if (! file.is_open()) --> error

  // Line reading loop
  while ( ! file.feof() )
    std::getline( file, line );
    std::cout << "Line read: " << line << std::endl;

  // file.close() or delegate to destructor


I am not being able to use this code,I dont know why.My project is an
ATL COM project with WTL support without MFC.So I am not able to use
CFile class also.will U plz get me a code for reading file line by
line using FILE text file will be having random number of
data such as
       ....//random nuber of lines.
Now I need to read each line of the file and save it into a string
variable and use this variable in the application.the problem here is
that I dont know How many lines will the file have.I am really
puzzled here with so many problems.Plz help me with code which will be
not using C++ I/O stream classes,will be using FILE structure,because
I am having problem with that.plz get me out of this situation as
early as possible b'coz my boss is screwing me now.Again thanks a lot
from my heart for your invaluable suggestions.

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