Question

i’m trying to write to append data to the end of a file, and am using the seekp(streamoff off, ios_base::seekdir dir) function but it doesn’t append, somehow it writes the data in the middle of the file.
i tried adding opening the file like this – file.open(resultFile,fstream::in|fstream::out);
(as was suggested in other similar posts) though i still get the same output.
that’s the code:

bool Manager::ValidCommand(Command* com, ofstream &ResultFile) const  
{  
    Employee::DepartmentEn dept = Employee::InvalidDepartment;  
       if (com == NULL)  
            return false;  
       if(com->GetFunction() <Command::PrintCityCouncilList || com->GetFunction() > Command::HireEmployee){  
            ResultFile.seekp(0,ios::end);  
            ResultFile << "Command:Failed activating function - invalid function number\n";  
            return false;}  
       if ((com->GetFunction() == Command::PrintDepartmentEmployees) || (com->GetFunction() == Command::PrintDepartmentExpenses) || (com->GetFunction() == Command::PrintDepartmentStatistics)){  
            dept = com->GetDepartment();  
       if((pcc->FindDepartment(dept) == NULL )|| (dept < Employee::Engineering) ||(dept > Employee::Sanitation))  
       {  
           ResultFile.seekp(0,ios::end);  
           ResultFile << "Command:Failed activating function - invalid department \n";  
           return false;  
       }  
   }  
   return true;  
}

what might i be doing wrong?

Answer 1

What is variable pcc doing in there as referenced in your code?

if((pcc->FindDepartment(dept) == NULL ) .....))  
       {  ....   }

Accordingly to this documentation on C++’s file input/output here and quoted

os::app All output operations are performed at the end of the file, appending the content to the current content of the file. This flag can only be used in streams open for output-only operations.

This implies, append will not work if both input/output mode is specified… can you confirm this? If that’s the case, it might be worthwhile to forget opening in text mode, and use binary mode instead….

Another thing – is the file definitely open for you to enable to seek, ResultFile.seekp(...)? Check on the value of the stream by flashing up a debug message something like this:

if (ResultFile.bad()) cout << "Bad stream!\n";