C++学习-IO流操作

#include <iostream>
using namespace std;
int main()
{
	cout << 1 << endl;
	cerr << 2 << endl;
	clog << 3 << endl;
	
	cout.put('I');
	cout << endl;
	cout.write("I love you", 8);
	cout << endl;
	system("pause");
	return 0;
}

#include<iostream>
#include <fstream>     //加上这样一个头文件，文件操作
using namespace std;

int main()
{
	fstream file;
	file.open("test.txt", ios::out);
	if (!file)
	{
		cout << "打开文件失败" << endl;
		exit(0);
	}
	file << "I love you" << endl;
	file << "but you don't love me" << endl;
	file.close();
	fstream file1;
	file1.open("test.txt", ios::in);
	if (!file1)
	{
		cout << "打开文件失败" << endl;
		exit(0);
	}
	char str[100];
	while (!file1.eof())
	{
		file1.getline(str, sizeof(str));
		cout << str << endl;
	}
	file1.close();
	system("pause");
	return 0;
}

#include <iostream>
#include <fstream>
#include <iomanip>
using namespace std;
struct student
{
	char name[10];
	int num;
	int age;
	char sex;
};


int main()
{
	student mystudent[3] = { "victor", 1001, 98, 'w',
		"我爱学习", 1002, 1, 'w',
		"落尘孤鹜", 1003, 55, 'm' };
	//fstream---ofstream---ifstream
	ofstream outfile("file.txt", ios::binary);
	if (!outfile)
	{
		cerr << "打开文件失败" << endl;
		return 0;
	}
	for (int i = 0; i < 3; i++)
	{
		//write("指针",大小)
		outfile.write((char *)&mystudent[i], sizeof(mystudent[i]));
	}
	outfile.close();
	ifstream infile("file.txt", ios::binary);
	if (!infile)
	{
		cerr << "打开文件失败" << endl;
		return 0;
	}
	student stu[3];
	for (int i = 0; i < 3; i++)
	{
		infile.read((char *)&stu[i], sizeof(stu[i]));
	}

	infile.close();
	cout << setw(10) << "姓名"
		<< setw(7) << "学号"
		<< setw(6) << "年龄"
		<< setw(6) << "性别" << endl;
	for (int i = 0; i < 3; i++)
	{
		cout << setw(10) << stu[i].name;
		cout << setw(7) << stu[i].num;
		cout << setw(6) << stu[i].age;
		cout << setw(6) << stu[i].sex << endl;
	}
	system("pause");
	return 0;
}

#include <iostream>
#include <fstream>
using namespace std;
struct student
{
	char name[10];
	int num;
	int age;
};
student stu[5] =
{
	"哇哦", 1001, 18,
	"孤鹜", 1002, 19,
	"闲者", 1003, 20,
	"路伴", 1004, 21,
	"victor", 1005, 22
};
int main()
{
	student mystudent;
	fstream file;
	//ios::binary  二进制形式  
	file.open("file.txt", ios::out | ios::in | ios::binary);
	if (!file)
	{
		cerr << "打开文件失败" << endl;
		exit(0);
	}
	for (int i = 0; i < 5; i++)
	{
		file.write((char *)&stu[i], sizeof(student));   //写的方式是怎样
	}
	file.seekp(sizeof(student)* 4);  //移动到第5个人位置
	file.read((char*)&mystudent, sizeof(student));
	cout << mystudent.name << "\t" << mystudent.num << "\t" << mystudent.age<<endl;

	file.seekp(sizeof(student)* 1, ios::beg);
	file.read((char*)&mystudent, sizeof(student));
	cout << mystudent.name << "\t" << mystudent.num << "\t" << mystudent.age << endl;

	file.close();
	system("pause"); 
	
	return 0;
}