Still celebrating National IT Professionals Day with 3 months of free Premium Membership. Use Code ITDAY17

x
?
Solved

Createfile and Sharing

Posted on 1997-04-16
1
Medium Priority
?
816 Views
Last Modified: 2011-10-03
I need to be able to reopen a file that already has handle open. I used Creatfile to open a text file and read it no problem....but I need to be able to reopen the file for writing without dropping the handling. if I drop the handle another function that is polling the file will grab it. I've tried to initially open the file with the FILE_SHARE_WRITE
attribute but this won't work. Is there anyway to Erase the file and move the file pointer back to the beginning without dropping the handle?
Here's a bit of the code that won't work

short int WriteFile(HANDLE *FHandle,char *buffer,CString                        ,*Filename,unsigned int *towrite)


      HANDLE newhandle;
      DWORD BytesWritten,faccess,fcreat,foattrib,fsmode;
      LPDWORD BWriteptr;
      BWriteptr=&BytesWritten;
      BOOL WriteSuccess,Closep,Closec;
      faccess=GENERIC_WRITE;
        fcreat=TRUNCATE_EXISTING;          
        foattrib=FILE_ATTRIBUTE_NORMAL;
        fsmode=FILE_SHARE_WRITE;
      //CloseHandle(*FHandle); in order for this to work I                                 have to close thishandle
      newhandle = CreateFile(*Filename,
                  faccess,//GENERIC_WRITE                                fsmode,//FILE_SHARE_WRITE,
                                   NULL,
                  fcreat,//TRUNCATE_EXISTING,
            foattrib,//FILE_ATTRIBUTE_NORMAL,
                                NULL);

    if ((newhandle) != (INVALID_HANDLE_VALUE))
      {
          WriteSuccess=
      WriteFile(newhandle,buffer,(*towrite),BWriteptr,NULL);            
          if (WriteSuccess)
          {
              //Closep=CloseHandle(*FHandle);
              Closec=CloseHandle(newhandle);
              if ((Closep) /*&& (Closec=)*/ )
                return 0;


Any ideas?

0
Comment
Question by:Brentg
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
1 Comment
 

Accepted Solution

by:
markusk earned 100 total points
ID: 1162755
If you first open the file, you should do this by:

LPCTSTR lpszFileName = "YourFile";
DWORD   fdwAccess = GENERIC_READ;     // | GENERIC_WRITE
DWORD   fdwShareMode = FILE_SHARE_READ | FILE_SHARE_WRITE;
DWORD   fdwCreate = OPEN_EXISTING;    // or what you want
DWORD   fdwAttrsAndFlags = FILE_ATTRIBUTE_NORMAL;
CreateFile (lpszName, fdwAccess, fdwShareMode, NULL, fdwCreate, fdwAttrsAndFlags, NULL);


The second call should look like the following code fragment:
LPCTSTR lpszFileName = "YourFile";
DWORD   fdwAccess = GENERIC_WRITE     // | GENERIC_READ
DWORD   fdwShareMode = FILE_SHARE_READ | FILE_SHARE_WRITE; // you must specfiy the FILE_SHARE_READ flag because the fist call to CreateFile opened the file in GENERIC_READ mode. If not, the function call will fail.
DWORD   fdwCreate = OPEN_EXISTING;    // or what you want
DWORD   fdwAttrsAndFlags = FILE_ATTRIBUTE_NORMAL;
CreateFile (lpszName, fdwAccess, fdwShareMode, NULL, fdwCreate, fdwAttrsAndFlags, NULL);

hope this will help...
0

Featured Post

Enroll in September's Course of the Month

This month’s featured course covers 16 hours of training in installation, management, and deployment of VMware vSphere virtualization environments. It's free for Premium Members, Team Accounts, and Qualified Experts!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Introduction This article is the first in a series of articles about the C/C++ Visual Studio Express debugger.  It provides a quick start guide in using the debugger. Part 2 focuses on additional topics in breakpoints.  Lastly, Part 3 focuses on th…
  Included as part of the C++ Standard Template Library (STL) is a collection of generic containers. Each of these containers serves a different purpose and has different pros and cons. It is often difficult to decide which container to use and …
The goal of the tutorial is to teach the user how to use functions in C++. The video will cover how to define functions, how to call functions and how to create functions prototypes. Microsoft Visual C++ 2010 Express will be used as a text editor an…
The viewer will learn additional member functions of the vector class. Specifically, the capacity and swap member functions will be introduced.

722 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question