CIS 250 File and formatting examples

Using I/O manipulators to format output

#include <iostream>
#include <iomanip>
using std::cout;
using std::fixed;
using std::left;
using std::right;
using std::setprecision;
using std::setw;

int main(int argc, char* argv[]) {
    const char* names[] = { "Theodore", "Melinda", "Sasquatch", "Sue" };
    double amts[] = { 37.5, 185.135, .2743, 409 };
    int ctr = 0;
    double sum = 0.0;

    cout << "Name        Amount\n";
    cout << "----------- ------\n";
    for (ctr=0; ctr<4; ctr++) {
        cout << setw(10) << left << names[ctr] << " " 
             << setw(7) << fixed << right << setprecision(2) << amts[ctr] << '\n';
        sum += amts[ctr];
    }
    cout << "----------- ------\n";
    cout << "Total      " << setw(7) << fixed << right << setprecision(2) << sum << '\n';


    return 0;
}

Using printf to format output

#include <cstdio>

int main(int argc, char* argv[]) {
    const char* names[] = { "Theodore", "Melinda", "Sasquatch", "Sue" };
    double amts[] = { 37.5, 185.135, .2743, 409 };
    int ctr = 0;
    double sum = 0.0;

    printf("Name        Amount\n");
    printf("----------- ------\n");
    for (ctr=0; ctr<4; ctr++) {
        printf("%-10s %7.2f\n", names[ctr], amts[ctr]);
        sum += amts[ctr];
    }
    printf("----------- ------\n");
    printf("Total      %7.2f\n", sum);


    return 0;
}

I/O manipulators used to format output to file

#include <fstream>
#include <iostream>
#include <iomanip>
using std::cout;
using std::fixed;
using std::left;
using std::ofstream;
using std::right;
using std::setprecision;
using std::setw;

int main(int argc, char* argv[]) {
    const char* names[] = { "Theodore", "Melinda", "Sasquatch", "Sue" };
    double amts[] = { 37.5, 185.135, .2743, 409 };
    int ctr = 0;
    double sum = 0.0;

    ofstream out("format3.txt");
    if (out) {
        out << "Name        Amount\n";
        out << "----------- ------\n";
        for (ctr=0; ctr<4; ctr++) {
            out << setw(10) << left << names[ctr] << " " 
                 << setw(7) << fixed << right << setprecision(2) << amts[ctr] << '\n';
            sum += amts[ctr];
        }
        out << "----------- ------\n";
        out << "Total      " << setw(7) << fixed << right << setprecision(2) << sum << '\n';
        out.close();
    }


    return 0;
}

Using sprintf (and snprintf) used to format output to file

#include <cstdio>
#include <fstream>
using std::ofstream;

int main(int argc, char* argv[]) {
    const char* names[] = { "Theodore", "Melinda", "Sasquatch", "Sue" };
    double amts[] = { 37.5, 185.135, .2743, 409 };
    char buf[300];
    int ctr = 0;
    double sum = 0.0;

    ofstream out("format4.txt");
    if (out) {

        snprintf(buf, 300, "Name        Amount\n");
        out << buf;
        snprintf(buf, 300, "----------- ------\n");
        out << buf;

        for (ctr=0; ctr<4; ctr++) {
            snprintf(buf, 300, "%-10s %7.2f\n", names[ctr], amts[ctr]);
            out << buf;
            sum += amts[ctr];
        }
        snprintf(buf, 300, "----------- ------\n");
        out << buf;
        snprintf(buf, 300, "Total      %7.2f\n", sum);
        out << buf;

        out.close();
    }

    return 0;
}

A simple tokenizer

#include <cstring>
#include <iostream>
#include <string>
using std::cout;
using std::string;

int main(int argc, char* argv[]) {
    char linein[] = "first name,last name,1234.56:sales";
    char* ptr;

    ptr = strtok(linein, ",:");
    while (ptr != NULL) {
        cout << ptr << '\n';
        ptr = strtok(NULL, ",:");
    }

    return 0;
}

/* token2.dat input file:

Theodore,37.5
Melinda,185.135
Sasquatch,.2743
Sue,409
*/

A tokenizer used to read fields from file records

#include <cstdlib>
#include <cstring>
#include <iostream>
#include <iomanip>
#include <fstream>
#include <string>
using std::cout;
using std::fixed;
using std::ifstream;
using std::left;
using std::right;
using std::setprecision;
using std::setw;
using std::string;

int main(int argc, char* argv[]) {
    double sum = 0.0;
    string line;
    char buf[300];
    
    ifstream infile("token2.dat");
    if (infile) {
        cout << "Name        Amount\n";
        cout << "----------- ------\n";
        getline(infile, line);
        while (infile) {
            strncpy(buf, line.c_str(), 300);
            char* ptr = strtok(buf, ",");
            string name(ptr);
            ptr = strtok(NULL, ",");
            double amount = atof(ptr);

            cout << setw(10) << left << name << " " 
                 << setw(7) << fixed << right << setprecision(2) << amount << '\n';
            sum += amount;
            getline(infile, line);
        }
        infile.close();

        cout << "----------- ------\n";
        cout << "Total      " << setw(7) << fixed << right << setprecision(2) << sum << '\n';
    }

    return 0;
}

Reading multiple fields from file records using iostream/ifstream

#include <cstdlib>
#include <cstring>
#include <iostream>
#include <iomanip>
#include <fstream>
#include <string>
using std::cout;
using std::fixed;
using std::ifstream;
using std::left;
using std::right;
using std::setprecision;
using std::setw;
using std::string;

int main(int argc, char* argv[]) {
    double sum = 0.0;
    string name;
    double amount;
    string strAmount;
    
    ifstream infile("token2.dat");
    if (infile) {
        cout << "Name        Amount\n";
        cout << "----------- ------\n";
        getline(infile, name, ',');
        while (infile) {
            getline(infile, strAmount);
            amount = atof(strAmount.c_str());

            cout << setw(10) << left << name << " " 
                 << setw(7) << fixed << right << setprecision(2) << amount << '\n';
            sum += amount;
            getline(infile, name, ',');
        }
        infile.close();

        cout << "----------- ------\n";
        cout << "Total      " << setw(7) << fixed << right << setprecision(2) << sum << '\n';
    }

    return 0;
}
/* format3.txt and format4.txt output files

Name        Amount
----------- ------
Theodore     37.50
Melinda     185.13
Sasquatch     0.27
Sue         409.00
----------- ------
Total       631.91
*/