Read and write in file

polopo

Hi All How can i read and write in .txt file in VC++(MFC)?Plz help me

singh

santhoshv84

Hi, You can use CFile, like this you open the file..

char* pszFileName = "c:\\test\\myfile.dat";
CFile myFile;
CFileException fileException;

if ( !myFile.Open( pszFileName, CFile::modeCreate |
CFile::modeReadWrite, &fileException ) )

like this you can read and write..

char szBuffer[256];
UINT nActual = 0;
CFile myFile;

myFile.Write( szBuffer, sizeof( szBuffer ) );
myFile.Seek( 0, CFile::begin );
nActual = myFile.Read( szBuffer, sizeof( szBuffer ) );

Like this you close the file..

myFile.Close();

The price of anything is the amount of life you exchange for it. Thanks and Regards. SANTHOSH V

_AnsHUMAN_

CStdioFile::ReadString CStdioFile::WriteString

Somethings seem HARD to do, until we know how to do them. ;-)_AnShUmAn_

polopo

i try both example but nothing is write in file..File is open but data is not write there? Plz help me

singh

toxcct

show your code dude !

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polopo

Thx's all I was wrong.. It's working.. THx's for help

singh

cpvc

Hi I more problem when new is came then old line is delete.But i don't want to delete old line..Plz help me

toxcct

cpvc++ wrote:

Plz help me

F*CK, you don't reply to my questions, and still you're asking for help ?!!! :mad:

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cpvc

Hey what question Man?I am asking first time..

toxcct

Does this post mean something to you ?[^]

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cpvc

Mr. toxcct

I am not Mr. polop which is start this thread.I am different user and it's post help me and i want some more help me..Sorry for missunderstanding any way my code is here..Pla help me

CStdioFile file;
if (file.Open("\\log.txt", CFile::modeCreate|CFile::modeWrite ))
{
file.WriteString(logfile);

	file.WriteString("\\n");
	
}
file.Close();

logfile is CString type which have some information.. Now i am able to write in file but old line is delete when new line write. Plz help me

toxcct

cpvc++ wrote:

I am not Mr. polop which is start this thread

sorry, I didn't notice that aspect of the things :) The problem in your code is that you're using CFile::modeCreate, but according to the documentation[^], this flag tells to truncate the file if already existing :

MSDN says:

CFile::modeCreate Directs the constructor to create a new file. If the file exists already, it is truncated to 0 length

So, you have to add the flag CFile::modeNoTruncate to counter this undesired behavior. The use of this flag however keeps the file pointer at the beginning of the file. So if you want to append things at the end, you must call once after CStdioFile::Open() the function CStdioFile::Seek(CFile::end). Does the following work better ?

CStdioFile file;
if (file.Open(_T("\\log.txt"), CFile::modeCreate | CFile::modeWrite | CFile::modeNoTruncate)) {
//file.Seek(0, CFile::end);
file.SeekToEnd();
file.WriteString(logfile);
file.WriteString(_T("\n"));
file.Close();
}

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modified on Thursday, September 4, 2008 6:46 AM

cpvc · modified on Thursday, September 4, 2008 6:46 AM

ok when i am useing your code then i am geting error..Plz help me

error C2660: 'CStdioFile::Open' : function does not take 1 arguments
error C2660: 'CStdioFile::Seek' : function does not take 1 arguments
error C2065: 'logfile' : undeclared identifier1>
error C2660: 'CStdioFile::Open' : function does not take 1 arguments
error C2660: 'CStdioFile::Seek' : function does not take 1 arguments
error C2065: 'logfile' : undeclared identifier

toxcct

god, I made a typo. you shouldn't have read

if (_T(file.Open("\\log.txt"), CFile::modeCreate | CFile::modeWrite | CFile::modeNoTruncate)) {

but this :

if (file.Open(_T("\\log.txt"), CFile::modeCreate | CFile::modeWrite | CFile::modeNoTruncate)) {

I fixed the previous post BTW. and sorry, I am at work, and I have no compiler, so I couldn't test it before posting...

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cpvc

i was read but i think both have make same mistake..And mistake is

file.Seek(CFile::end)

this is not right and right one is this

file.Seek(0,CFile::end)

Any way thxs for help..

toxcct

cpvc++ wrote:

this is not right and right one is this file.Seek(0,CFile::end)

Yes you're right. BTW, you still can call CFile::SeekToEnd() which takes no parameters, and moves directly to the end of file. anyway, does it work now for you ?

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