Clear contents of a Text File

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I am working on a sever/client applicataion. I want to maintain information of all active clients in a text file named "Information.txt". I update this text file after every 3 seonds. So, I want the text file to clear all of its contents after every 3 seconds without deleting the file. Is there any way to do it ? :( I don't want to use freopen().

Posted 10-Apr-13 0:49am

ayesha hassan

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CHill60 10-Apr-13 6:54am

~~can't remember the syntax off the top of my head, but isn't~~ there is an option when you open the file to open for write (which effectively clears the contents) rather than append - see http://www.cprogramming.com/tutorial/cfileio.html

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Matthew Faithfull · Answer 1 · 2013-04-10T00:54:00

Solution 1

Don't bother, just use seek to return the file pointer to the beggining of the file and then write an EOF if you want to.
On Win32 there's an API to set the extent of the file which you could use to prevent anything reading past that EOF even if it chose to. That's not necessary though if your code is in full control of the file.

Posted 10-Apr-13 0:54am

Matthew Faithfull

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ayesha hassan 10-Apr-13 7:13am

fpFile = fopen("sendclInformation.txt", "r+");
fseek(fpFile, 0, SEEK_SET);
WriteFile(file,EOF,strlen(EOF),&dwWritten,0);

I tried this but:
error C2664: 'strlen' : cannot convert parameter 1 from 'int' to 'const char *'

Matthew Faithfull 10-Apr-13 7:18am

You need to open with write permission to start with then don't use strlen with EOF, EOF is numeric constant the size of a TCHAR so use something like:
WriteFile( file, EOF, sizeof(TCHAR), &dwWritten, 0 );

ayesha hassan 10-Apr-13 7:21am

and now the error:
error C2664: 'WriteFile' : cannot convert parameter 2 from 'int' to 'LPCVOID'

Matthew Faithfull 10-Apr-13 7:36am

My bad I forget the signature for WriteFile, change EOF for reinterpret_cast< const void*>(EOF) . Messy but should work.

TrushnaK · Answer 2 · 2013-04-10T00:55:00

Solution 2

open the file with stream reader then write nothing
like:-

Const ForWriting = 2

Set objFSO = CreateObject("Scripting.FileSystemObject")
Set objFile = objFSO.OpenTextFile("C:\Scripts\Test.txt", ForWriting)

objFile.Write ""
objFile.Close

Posted 10-Apr-13 0:55am

TrushnaK