8.2 文件输入输出

书中页数：P285
代码名称：fileIO.cc

#include <iostream>
using std::cerr; using std::cout; using std::endl;

#include <fstream>
using std::ifstream;

#include <string>
using std::string;

#include <stdexcept>
using std::runtime_error;

void process(ifstream &is)
{
	string s;
	while (is >> s)
		cout << s << endl;
}

int main(int argc, char* argv[])
{
	// for each file passed to the program
	for (auto p = argv + 1; p != argv + argc; ++p) {
		ifstream input(*p);   // create input and open the file
		if (input) {          // if the file is ok, ``process'' this file
			process(input);
		}
		else
			cerr << "couldn't open: " + string(*p);
	} // input goes out of scope and is destroyed on each iteration

	auto p = argv + 1, end = argv + argc;

	ifstream input;
	while (p != end) {        // for each file passed to the program
		input.open(*p);       // open the file, automatically clears the stream 
		if (input) {          // if the file is ok, read and ``process'' the input
			process(input);
		}
		else
			cerr << "couldn't open: " + string(*p);
		input.close();        // close file when we're done with it
		++p;                  // increment pointer to get next file
	}

	return 0;
}