Hello,
I am trying to read a log file which is written by another application.
Other application is running,and writing lines to log file time to time.
At the same time I supposed to read log file without lose and as soon as modification occurs.
Even I check if the error occurs when opening file,
I can not get the line written when open file error occurs.
But it can not get some lines of the log file.
Below you can find the function which I am using to accomplish this job.
Thanks a lot
p.s. : I can not modify the other application.
| while(1) |
| { |
| loopTry++; |
| if(CFile::GetStatus(fileName,filestatus)) |
| { |
| if(filestatus.m_size > lastSize) |
| { |
| if ( !myFile.Open( fileName, CFile::shareDenyWrite | // |
| CFile::modeRead , &fileException ) ) |
| { |
| CString cs; cs.Format(_T("Can't open file %s, error = %u readTry = %d"), |
| fileName, fileException.m_cause,readTry ); |
| log(cs); |
| |
| } |
| else//oku |
| { |
| readTry++; |
| char * rBuffer = ::new char[filestatus.m_size+1-cursorPos]; |
| rBuffer[filestatus.m_size-cursorPos] = '\0'; |
| |
| //READ START |
| myFile.LockRange(0,filestatus.m_size);// |
| myFile.Seek(cursorPos, CFile::begin);//TODO: compare seek overhead with reading up to cursorPos |
| myFile.Read(rBuffer,filestatus.m_size-cursorPos); |
| myFile.UnlockRange(0,filestatus.m_size); |
| myFile.Close(); |
| //READ END |
| lastSize = filestatus.m_size; |
| //PROCESS START |
| std::string str(rBuffer); |
| int lineEndPos = 0; |
| int localCursor = 0; |
| for(;;) |
| { |
| std::string line; |
| |
| |
| int lastNewlineIndex = str.find("\r\n",lineEndPos+1); |
| if(lastNewlineIndex == std::string::npos)//if there is no newline left |
| { |
| break; |
| } |
| lineEndPos = lastNewlineIndex; |
| line = str.substr(localCursor,lineEndPos-localCursor); |
| ProcessLine(line,loopTry,readTry);// some func to process line read |
| localCursor = lineEndPos + 2; |
| cursorPos += localCursor; |
| } |
| //PROCESS END |
| ::delete [] rBuffer; |
| } |
| } |
| else//file size is not changed. wait { |
| Sleep(wait); |
| } |
| } |
| else |
| { |
| CString cs; cs.Format(_T("can not get status. looptry = %d"),loopTry ); |
| log(cs); |
| } |
| } |
