fstream open parameters

**Ancient Dragon** · 01-26-2006

using VC++ .NET 2005 Express Edition on XP. I thought the open function only takes two parameters, but I'm apparently wrong. What is the third parameter? I looked at several fstream tutorials but none of them show a third parameter.

I came across this problem purely by accident -- the compiler compiled the code without complaint, but the program crashed on that line.

Code:

fstream a;
a.open(filename,ios::in | ios::out , ios::binary | ios::ate);

The comma in the above line should have been an or operator |.

**Quantum1024** · 01-26-2006

Open dose indeed only take two paramaters. Make sure your first paramater is an array of chars and not a string object.

**Ancient Dragon** · 01-26-2006

Here is the complete program

Code:

#include "stdafx.h"
#include <fstream>
using namespace std;

int _tmain(int argc, _TCHAR* argv[])
{
	char file[255];
	fstream a;
	strcpy(file,"mel.txt");
	a.open(file,ios::in|ios::out, ios::binary|ios::ate);
	a.close();
	a.clear();
	return 0;
}

here is stdafx.h

Code:

// stdafx.h : include file for standard system include files,
// or project specific include files that are used frequently, but
// are changed infrequently
//

#pragma once

#define WIN32_LEAN_AND_MEAN		// Exclude rarely-used stuff from Windows headers
#include <stdio.h>
#include <tchar.h>



// TODO: reference additional headers your program requires here

**ZuK** · 01-27-2006

open did in fact have 3 parameters as defined in the heder <fstream.h>

Code:

        filebuf*        open(const char *, int, int = filebuf::openprot);

could not find anything in <fstream> but if I see "stdafx.h" in any source I don't wonder much.

Kurt

**Dave_Sinkula** · 01-27-2006

http://msdn.microsoft.com/library/de....3a3a.open.asp

Later fixed - http://msdn.microsoft.com/library/de...ementation.asp

In the new Standard C++ iostream library:

open functions do not take a third parameter (the protection parameter).

[edit]Hmm - iostream, not fstream, but I think it's the same type of thing. And I think MS now uses Dinkumware.

**Ancient Dragon** · 01-27-2006

Thanks for the links.

Originally Posted by MSDN

open functions do not take a third parameter (the protection parameter).

Than I wonder why the compiler accepts it? Or whey the open function doesn't just ignore it if its present?

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