Open File

[mom.klaib]

Hi
I am a student doing a project using C++ builder. I hava a problem in
opening a number of files more than 47, when run it only it create 46
file, Please help me to be able to create any number of files. Thanks
to your efforts.
Mohd Klaib
Example :

FILE *out[100];
char filename[100];
int noFiles=78;

for (int i=0 ; i<noFiles ; i++)
{
sprintf (filename,"c:/test/TestSuite%d",i) ;
out[i]= fopen(filename, "wt");
}

[Ian Collins]

mo*******@gmail .com wrote:

Hi
I am a student doing a project using C++ builder. I hava a problem in
opening a number of files more than 47, when run it only it create 46
file, Please help me to be able to create any number of files. Thanks
to your efforts.
Mohd Klaib
Example :

FILE *out[100];
char filename[100];
int noFiles=78;

for (int i=0 ; i<noFiles ; i++)
{
sprintf (filename,"c:/test/TestSuite%d",i) ;
out[i]= fopen(filename, "wt");
}

This looks more like a C problem.

There isn't a lot you can do if you have hit the number of open files
limit for your system. You would be better off asking on a platform
specific group.

--
Ian Collins.

[John Harrison]

mo*******@gmail .com wrote:

Hi
I am a student doing a project using C++ builder. I hava a problem in
opening a number of files more than 47, when run it only it create 46
file, Please help me to be able to create any number of files. Thanks
to your efforts.
Mohd Klaib
Example :

FILE *out[100];
char filename[100];
int noFiles=78;

for (int i=0 ; i<noFiles ; i++)
{
sprintf (filename,"c:/test/TestSuite%d",i) ;
out[i]= fopen(filename, "wt");
}

Do you really have to have 78 files open *simultaneously *? That's hard
to believe. I suggest you operate on the files one at a time, and close
them when you are finished. Reorganise your code to do this.

john

[James Kanze]

On May 28, 9:00 am, John Harrison <john_androni.. [e-mail] ote:

mom.kl...@gmail .com wrote:

I am a student doing a project using C++ builder. I hava a problem in
opening a number of files more than 47, when run it only it create 46
file, Please help me to be able to create any number of files. Thanks
to your efforts.

Example :

FILE *out[100];
char filename[100];
int noFiles=78;

for (int i=0 ; i<noFiles ; i++)
{
sprintf (filename,"c:/test/TestSuite%d",i) ;
out[i]= fopen(filename, "wt");
}

Do you really have to have 78 files open *simultaneously *? That's hard
to believe.

For a student project, maybe, but there's nothing particularly
extraordinary for a server to have several hundred files open
simultaneously.

I suggest you operate on the files one at a time, and close
them when you are finished.

That would mean opening the files for each request, and closing
it at the end of the request. Which would slow things down
considerably, and wouldn't necessarily help, since different
threads (different client connections) will still access
different files.

--
James Kanze (GABI Software) email:ja******* **@gmail.com
Conseils en informatique orientée objet/
Beratung in objektorientier ter Datenverarbeitu ng
9 place Sémard, 78210 St.-Cyr-l'École, France, [phone]

[kingfox]

On 5ÔÂ28ÈÕ, ÏÂÎç2ʱ07·Ö, mom.kl...@gmail .com wrote:

Hi
I am a student doing a project using C++ builder. I hava a problem in
opening a number of files more than 47, when run it only it create 46
file, Please help me to be able to create any number of files. Thanks
to your efforts.
Mohd Klaib
Example :

FILE *out[100];
char filename[100];
int noFiles=78;

for (int i=0 ; i<noFiles ; i++)
{
sprintf (filename,"c:/test/TestSuite%d",i) ;
out[i]= fopen(filename, "wt");
}

Maybe you can use Windows API e.g. OpenFile(...). But I don't know how
much files can be opened simultaneously by this API.

[kingfox]

On 5ÔÂ28ÈÕ, ÏÂÎç8ʱ01·Ö, kingfox <foxap...@gmail .comwrote:

On 5ÔÂ28ÈÕ, ÏÂÎç2ʱ07·Ö, mom.kl...@gmail .com wrote:

Hi
I am a student doing a project using C++ builder. I hava a problem in
opening a number of files more than 47, when run it only it create 46
file, Please help me to be able to create any number of files. Thanks
to your efforts.
Mohd Klaib
Example :

FILE *out[100];
char filename[100];
int noFiles=78;

for (int i=0 ; i<noFiles ; i++)
{
sprintf (filename,"c:/test/TestSuite%d",i) ;
out[i]= fopen(filename, "wt");
}

Maybe you can use Windows API e.g. OpenFile(...). But I don't know how
much files can be opened simultaneously by this API.- Òþ²Ø±»ÒýÓÃÎÄ×Ö -

- ÏÔʾÒýÓõÄÎÄ×Ö -

I just wrote a program to test how many files can be opened by Windows
API - OpenFile. This program open more than 5000 files simultaneously.
So I think OpenFile can fit your request. The program as below:

//--------------------------------------------------------------------------------------------------
#include <iostream>
#include <vector>
#include <sstream>
using namespace std;
#include <windows.h>

void closeFilesByAPI (HANDLE fileHandle)
{
CloseHandle(fil eHandle);
}

void howManyFilesCan BeOpenedByAPI()
{
vector<HANDLEha ndleVector;
HANDLE fileHandle;
int count = 0;
DWORD writtenBytes;
do {
stringstream fileName;
fileName.clear( );
fileName << "file" << count;
fileHandle = CreateFile(file Name.str().c_st r(), GENERIC_WRITE,
FILE_SHARE_WRIT E, NULL, CREATE_NEW, FILE_ATTRIBUTE_ NORMAL
+FILE_FLAG_RAND OM_ACCESS, NULL);
if (fileHandle == INVALID_HANDLE_ VALUE)
break;
handleVector.pu sh_back(fileHan dle);
WriteFile(fileH andle, fileName.str(). c_str(),
fileName.str(). size(), &writtenByte s, NULL);
cout << fileName.str() << '\r';
count ++;
}while(fileHand le != INVALID_HANDLE_ VALUE);
cout << "Total number of files opened by ofstream is: " << count <<
endl;
for_each(handle Vector.begin(), handleVector.en d(),
closeFilesByAPI );
}
//--------------------------------------------------------------------------------------------------

[Michael DOUBEZ]

mo*******@gmail .com a écrit :

Hi
I am a student doing a project using C++ builder. I hava a problem in
opening a number of files more than 47, when run it only it create 46
file, Please help me to be able to create any number of files. Thanks
to your efforts.

You can have a look at the _NFILE defines in stdio.
It should give you the maximum number of file you can open with fopen.

Try to display errno and associated error with perror upon open failure.
It can help you identify the problem.

In your program:

sprintf (filename,"c:/test/TestSuite%d",i) ;
out[i]= fopen(filename, "wt");
if(out[i]<=0)
{//error
perror(filename );
}

Michael

[Jerry Coffin]

In article <R5************ *****@newsfe7-gui.ntli.net>,
jo************* @hotmail.com says...

[ ... ]

Do you really have to have 78 files open *simultaneously *? That's hard
to believe. I suggest you operate on the files one at a time, and close
them when you are finished. Reorganise your code to do this.

On many systems, opening or closing a file is a fairly expensive
operation, so this is likely to have a significant performance penalty.

It's technically off-topic, but most standard libraries I've looked at
had this limit set in a fairly easy-to-find definition. Adjust the
definition, re-compile the library, and you're off and running.

As long as we're off-topic: elsethread OpenFile was mentioned. MS
considers this obsolete, and new code is encouraged to use CreateFile
instead (though OpenFile probably isn't any more likely to disappear any
time soon than parts of C++ that have been deprecated...)

--
Later,
Jerry.

The universe is a figment of its own imagination.

[Jack Klein]

On Mon, 28 May 2007 18:24:47 +1200, Ian Collins <ia******@hotma il.com>
wrote in comp.lang.c++:

mo*******@gmail .com wrote:

Hi
I am a student doing a project using C++ builder. I hava a problem in
opening a number of files more than 47, when run it only it create 46
file, Please help me to be able to create any number of files. Thanks
to your efforts.
Mohd Klaib
Example :

FILE *out[100];
char filename[100];
int noFiles=78;

for (int i=0 ; i<noFiles ; i++)
{
sprintf (filename,"c:/test/TestSuite%d",i) ;
out[i]= fopen(filename, "wt");
}

This looks more like a C problem.

Looks like an obstructionist problem.

Wait, let me double check...

Yes, both sprintf() and fopen() are defined in the latest version of
the C++ standard.

In fact with addition of:

#include <cstdio>
#include <cstring>
using namespace std;

....and placement inside a suitable function, the user's snippet is
100% perfectly conforming standard C++ code.

Even with the addition of:

#include <stdio.h>
#include <string.h>

....the code is conforming, although deprecated.

There isn't a lot you can do if you have hit the number of open files
limit for your system. You would be better off asking on a platform
specific group.

Your advice is quite correct, but your comment is completely
incorrect. If you don't like using standard C++ library functions
that happen to be inherited from C, that's fine and dandy.

But no use of a function defined by the C++ standard is a "C problem".

Believe it or not, the C standard says absolutely nothing at all about
the behavior of fopen() or sprintf() in a C++ program. Anything and
everything in a C++ program is off-topic in C language groups.

The fact that C++ defines some functions with the same names as those
in the C library, and defines them to accept similar parameters and
return similar values, does not make them C functions when used in a
C++ program.

--
Jack Klein
Home: http://JK-Technology.Com
FAQs for
comp.lang.c http://c-faq.com/
comp.lang.c++ http://www.parashift.com/c++-faq-lite/
alt.comp.lang.l earn.c-c++
http://www.club.cc.cmu.edu/~ajo/docs/FAQ-acllc.html

[Markus Schoder]

On Mon, 28 May 2007 18:56:38 -0500, Jack Klein wrote:

Even with the addition of:

#include <stdio.h>
#include <string.h>

...the code is conforming, although deprecated.

Why should this be conforming? These are implementation specific header
files that need not work with anything but the specific C compiler they
are part of.

Of course in practice many vendors offer C and C++ compilers and design
there C system header files in such a way that they are compatible with
their C++ compiler but that is certainly not a requirement of either the
C or C++ standard.

--
Markus Schoder