I/O with strings

The object of my program is to read one line from a file, read a line from another file, compare the two and if file 1 is smaller than file 2, then it is supposed to write from file 1 to the output line and read a new line from file 1. Otherwise, it writes the line from file 2 to the output file and reads a new line from file 2. The program is supposed to do this while the end of neither file 1 of file 2 has been reached. Then if there is any line in file 1 or file 2 that still has not been written to the output file, the program should write those lines. Here is my code:

Code:

---

#include <iostream>
#include <iomanip>
#include <cmath>
#include <cstdlib>   
#include <fstream> 
#include <cstring> 
#include <string>

using namespace std;

int openFile(fstream& f, fstream& f1, fstream& f2);//function to open the files
void readWriteData(fstream& f, fstream& f1, fstream& f2);//function to read and write data


int main()
{
    fstream outFile; //output
    fstream inFile1;//input
    fstream inFile2;//input
   
    openFile(outFile, inFile1, inFile2);
    cin.get();
    return 0;   
}


int openFile(fstream& outFile, fstream& inFile1, fstream& inFile2)
{
    char outName[50];//storage of user input filename for the data file that is to be written to
    char inName1[50];//storage of user input filename for the first data file that is to be read from
    char inName2[50];//storage of user input filename for the second data file that is to be read from
   
    cout << "Please type the name of the first input file, including the extension: ";//requests user input of filename
    cin >> inName1;
    cout <<'\n';
    inFile1.open(inName1, ios::in); 
    if (inFile1.fail())//if file cannot be opened, a message will display
        {
            cerr << "Could not open " << inName1 << "!" << endl;
            return EXIT_FAILURE;
        }
   
    cout << "Please type the name of the second input file, including the extension: ";//requests user input of filename
    cin >> inName2;
    cout <<'\n';
    inFile2.open(inName2, ios::in);
    if (inFile2.fail())//if file cannot be opened, a message will display
        {
            cerr << "Could not open " << inName2 << "!" << endl;
            return EXIT_FAILURE;
        }   
       
    cout << "Please type the name of the output file, including the extension: ";//requests user input of filename
    cin >> outName;
    cout <<'\n';
    outFile.open(outName, ios::out);
    if (outFile.fail())//if file cannot be opened, a message will display
        {
            cerr << "Could not open " << outName << "!" << endl;
            return EXIT_FAILURE;
        }
 
    readWriteData(outFile, inFile1, inFile2);
    return 0;
   
}
void readWriteData(fstream& outFile, fstream& inFile1, fstream& inFile2)
{
    string in1;
    string in2;
 
        do
      {
                  getline(inFile1, in1);
                  getline(inFile2, in2);
         
            if (strcmp(in1.c_str(), in2.c_str()) < 0)
            {
                outFile << in1 << '\n';
                                outFile << in2 << '\n'; 
                        }
             
            else if (strcmp(in1.c_str(), in2.c_str()) > 0)
                          {       
                    outFile << in2 << '\n';
                outFile << in1 << '\n'; 
                          }
                        else if (strcmp(in1.c_str(), in2.c_str()) == 0)
                        {
                outFile << in1 << '\n';
                                outFile << in2 << '\n'; 
                        }
                }
          while (!inFile2.eof() || !inFile1.eof());
         
          inFile1.close();
      inFile2.close();
      outFile.close();
}

---

When I use this code, there are duplicate lines put to the output file. If I use this code:

Code:

---

#include <iostream>
#include <iomanip>
#include <cmath>
#include <cstdlib>   
#include <fstream> 
#include <cstring> 
#include <string>

using namespace std;

int openFile(fstream& f, fstream& f1, fstream& f2);//function to open the files
void readWriteData(fstream& f, fstream& f1, fstream& f2);//function to read and write data


int main()
{
    fstream outFile; //output
    fstream inFile1;//input
    fstream inFile2;//input
   
    openFile(outFile, inFile1, inFile2);
    cin.get();
    return 0;   
}


int openFile(fstream& outFile, fstream& inFile1, fstream& inFile2)
{
    char outName[50];//storage of user input filename for the data file that is to be written to
    char inName1[50];//storage of user input filename for the first data file that is to be read from
    char inName2[50];//storage of user input filename for the second data file that is to be read from
   
    cout << "Please type the name of the first input file, including the extension: ";//requests user input of filename
    cin >> inName1;
    cout <<'\n';
    inFile1.open(inName1, ios::in); 
    if (inFile1.fail())//if file cannot be opened, a message will display
        {
            cerr << "Could not open " << inName1 << "!" << endl;
            return EXIT_FAILURE;
        }
   
    cout << "Please type the name of the second input file, including the extension: ";//requests user input of filename
    cin >> inName2;
    cout <<'\n';
    inFile2.open(inName2, ios::in);
    if (inFile2.fail())//if file cannot be opened, a message will display
        {
            cerr << "Could not open " << inName2 << "!" << endl;
            return EXIT_FAILURE;
        }   
       
    cout << "Please type the name of the output file, including the extension: ";//requests user input of filename
    cin >> outName;
    cout <<'\n';
    outFile.open(outName, ios::out);
    if (outFile.fail())//if file cannot be opened, a message will display
        {
            cerr << "Could not open " << outName << "!" << endl;
            return EXIT_FAILURE;
        }
 
    readWriteData(outFile, inFile1, inFile2);
    return 0;
   
}
void readWriteData(fstream& outFile, fstream& inFile1, fstream& inFile2)
{
    string in1;
    string in2;
 
        do
      {
                  getline(inFile1, in1);
                  getline(inFile2, in2);
         
            if (strcmp(in1.c_str(), in2.c_str()) < 0)
            {
                outFile << in1 << '\n';
                                outFile << in2 << '\n'; 
                        }
             
            else if (strcmp(in1.c_str(), in2.c_str()) > 0)
                          {       
                    outFile << in2 << '\n';
                outFile << in1 << '\n'; 
                          }
                        else if (strcmp(in1.c_str(), in2.c_str()) == 0)
                        {
                outFile << in1 << '\n';
                                outFile << in2 << '\n'; 
                        }
                }
          while (!inFile2.eof() && !inFile1.eof());
         

          do
          {
                  if (inFile1.eof())
                        {
                                getline(inFile2, in2);
                                outFile << in2 << '\n';
                        }
                  else if (inFile2.eof())
                  {
                                getline(inFile1, in1);
                                outFile << in1 << '\n';

                  }
                }
          while (!inFile2.eof() || !inFile1.eof());
          inFile1.close();
      inFile2.close();
      outFile.close();
}

---

There are no duplicates but then the remainder of the output is not alphabetical. Does anyone know of a better way I can achieve what I want to do?

C++ strings can be compared directly - and your comparisons are a bit overcomplicated - so simplified I'd do like this:

Code:

---

// Since equal strings can be in "either order" and still be correct, we just let the first case handle that.
            if (in1 <= in2)
            {
                outFile << in1 << '\n';
                outFile << in2 << '\n'; 
            }
            else
            {       
                  outFile << in2 << '\n';
                  outFile << in1 << '\n'; 
            }

---

There is no need to get the C-string from a C++ string to compare the strings.

If you still insist on using c_str() to get the string, why not do:

Code:

---

// Since equal strings doesn't matter, just cover this case here, rather than
// a separate case.

          if (strcmp(in1.c_str(), in2.c_str()) <= 0)
          {
              outFile << in1 << '\n';
                outFile << in2 << '\n'; 
          }
// As the only other alternative, we swap the strings. No need to compare the strings - they haven't changed.
          else
          {       
                outFile << in2 << '\n';
                outFile << in1 << '\n'; 
          }

---

This way, at least you are not comparing the same string up to 3 times (the compiler MAY realize that the strcmp() function always returns the same thing for the same input, but that's far from guaranteed).

I prefer the first code-sequence.

--
Mats