7、C++ Primer 4th 笔记，标准IO库(2)

// for each file in the vector
while (it != files.end()) {
	ifstream input(it->c_str()); // open the file;
	// if the file is ok, read and "process" the input
	if (!input)
		break; // error: bail out!
	while(input >> s) // do the work on this file
		process(s);
	++it; // increment iterator to get
	next file
}
//check out the difference between these two programs.
ifstream input;
vector<string>::const_iterator it = files.begin();
// for each file in the vector
while (it != files.end()) {
	input.open(it->c_str()); // open the file
	// if the file is ok, read and "process" the input
	if (!input)
		break; // error: bail out!
	while(input >> s) // do the work on this file
		process(s);
	input.close(); // close file when we're done with it
	input.clear(); // reset state to ok
	++it; // increment iterator to get next file
}

string line, word; // will hold a line and word from input,respectively
while (getline(cin, line)) 
{ // read a line from theinput into line
		// do per-line processing
	istringstream stream(line); // bind to stream to the line we read
		while (stream >> word)
		{ // read a word from line
			// do per-word processing
		}
}

int val1 = 512, val2 = 1024;
ostringstream format_message;
// ok: converts values to a string representation
format_message << "val1: " << val1 << "\n"
               << "val2: " << val2 << "\n";
//the following is how to read
//str member obtains the string associated with a stringstream
istringstream input_istring(format_message.str());
string dump; // place to dump the labels from the formatted message
// extracts the stored ascii values, converting back to arithmetic types
input_istring >> dump >> val1 >> dump >> val2;
cout << val1 << " " << val2 << endl; // prints 512 1024