C++ file-redirection

Question

For faster input, I read that you can do file-redirection and include a file with the cin inputs already set.

In theory it should be used l

Answer 1

[I am just explaining the command line argument used in Question]

You can provide file name as command line input to the executible, but then you need to open them in your code.

Like

You have supplied two command line arguments namely inputfile & outputfile

[ App.exe inputfile outputfile ]

Now in your code

#include
#include
#include

int main(int argc, char * argv[])
{
   //argv[0] := A.exe
   //argv[1] := inputFile
   //argv[2] := outputFile

   std::ifstream vInFile(argv[1],std::ios::in); 
   // notice I have given first command line argument as file name

   std::ofstream vOutFile(argv[2],std::ios::out | std::ios::app);
   // notice I have given second command line argument as file name

   if (vInFile.is_open())
   {
     std::string line;

     getline (vInFile,line); //Fixing it as per the comment made by MSalters

     while ( vInFile.good() )
     {
         vOutFile << line << std::endl;
         getline (vInFile,line);          
     }
     vInFile.close();
     vOutFile.close();
  }

  else std::cout << "Unable to open file";

  return 0;
}