simple/trivial exercise for doing a file IO task and sorting the results.

fieIOAndSort.cpp

/***********************************
 * A demonstration of File IO and loops
 * This program will read from a file,
 * parse the line data into tokens.
 * sort the data, and write to a file.
 *
 * Author: Matt Mickelson
 * Original Files/Concepts: Dave Dalsveen
 */

#include <iostream>
#include <fstream>
#include <string>
#include <sstream>
#include <algorithm>

using namespace std;

const int ARRAY_SZ = 40;

struct Element{
    int number;
    double atomicWeight;
    string name;
};

/**
 * Used by the sort function to compare Element structs..
 */
bool compareAtomicWeight(const Element& elementOne,
   const Element & elementTwo ){
      return  elementOne.atomicWeight < elementTwo.atomicWeight;
}
/**
 * The main function takes in the command line arguments.
 * argc is the number of arguments.
 * argv is an array of character strings.
 */
int main(int argc, char *argv[]) {
    string s; // A string to hold the input
    int count = 0;
    Element elementArray[ARRAY_SZ];
    string sArray[ARRAY_SZ];
    stringstream inputStr;
    string token;

    // Check for the proper number of command line args.
    if (argc < 3) {
        cout << "usage: FileIO inputfile outputfile" << endl;
        return (EXIT_FAILURE);
    }
    // Outputs the command line
    for (int i = 0; i < argc; i++) {
        cout << "argv[" << i << "]=" << argv[i] << endl;
    }
    // Try to do the file IO

    //ifstream inFile("c:/inFile.txt");
    // argv[1] is the input file name

    ifstream inFile(argv[1]);
    
    if (inFile.is_open()) {

        //the sentinnel value is eof()
        while (!inFile.eof()) {

            //gets an entire line
            getline(inFile, s);
            inputStr << s;
            int tokCnt = 0;
            while ( getline(inputStr, token, ',') ){
                 sArray[tokCnt] = token;
                 tokCnt++;
            }

        // store the tokens to the Element Array Element
        elementArray[count].atomicWeight = atof(sArray[1].c_str());
        elementArray[count].number = atoi(sArray[0].c_str());
        elementArray[count].name = sArray[2];

        inputStr.clear();
            
            count++;
        }//end while inFile
        cout << "Line Count = " << count << endl;
        inFile.close();


        //do the actual sort
        sort(elementArray, elementArray + count - 1,compareAtomicWeight);

        // output the sorted data to a file
        ofstream outFile(argv[2]);

        if (outFile.is_open()) {
            for (int i = 0; i < count; i++) {

                outFile << elementArray[i].name<< ":" <<elementArray[i].number <<":"
                  << elementArray[i].atomicWeight <<"\r\n";

            }

            outFile.close();
        }// end if output open
    }// end if input open
    else {
        cout << "Input file can't be opened:" << argv[1] << endl;
        return (EXIT_FAILURE);
    }


    return (EXIT_SUCCESS);

}