concatenating files

Bjarne Stroustrup “Programming Principles and Practice Using C++”
Chapter 10 Exercise 8
Using std_lib_facilities.h by Bjarne Stroustrup.

[code language=”cpp”]
// Philipp Siedler
// Bjarne Stroustrup’s PPP
// Chapter 10 Exercise 8

#include "std_lib_facilities.h"

string read_file(string& _input) {
ifstream ist{ _input };
string result;
if (!ist) error("can’t open input file ", _input);
ist.exceptions(ist.exceptions() | ios_base::badbit);

ist >> result;
return result;
}

void write_file(string& _output, string& _input_1, string& _input_2) {
ofstream ost{ _output };
if (!ost) error("can’t open output file", _output);

ost << read_file(_input_1) + read_file(_input_2);
}

void calculate() {
string input_1 = "ch10_8_input_1.txt";
string input_2 = "ch10_8_input_2.txt";
string output = "ch10_8_output_1+2.txt";

cout << "Combining files " << input_1 << " & " << input_2 << "…";
write_file(output, input_1, input_2);
cout << " Done!" << endl;
cout << output << " successfully written." << endl;
}

int main()
try
{
calculate();

keep_window_open();
}
catch (runtime_error e) {
cout << e.what() << endl;
keep_window_open();
}
catch (…) {
cout << "Exiting" << endl;
keep_window_open();
}
[/code]

Output:
Combining files ch10_8_input_1.txt & ch10_8_input_2.txt...can't open input file ch10_8_input_2.txt
Please enter a character to exit

Input-File 1: ch10_8_input_1.txt
000

Input-File 2: ch10_8_input_2.txt
111

Output-File: ch10_8_output_1+2.txt
000
111