C++ IO设备读写功能实现详解

#include<iostream>
#include<windows.h>
#include<fstream>
using namespace std;
int main() {
	ofstream outfile;
	string name;
	int age;
	cin >> name >> age;
	outfile.open("C:/Users/98207/desktop/test.txt", ios::out);  // 写入文件，没有文件会新建
	outfile << name << endl;
	outfile << age;
	outfile.close();  // 文件结束需要关闭
	return 0;
}

#include<iostream>
#include<windows.h>
#include<string>
#include<fstream>
using namespace std;
int main() {
	ifstream infile;
	string str;
	int age;
	infile.open("C:/Users/98207/desktop/test.txt", ios::in);  // 读取文件
	while (1) {
		if (infile.eof()) {
			break;
		}
		infile >> str;
		cout << str << endl;;
		// getline(infile, str);
		// cout << str << endl;
	}
	infile .close();
	return 0;
}

#include<iostream>
#include<windows.h>
#include<string>
#include<fstream>
using namespace std;
int main() {
	string name;
	int age;
	fstream outfile;
	outfile.open("C:/Users/98207/Desktop/test2.txt", ios::out);
	cin >> name >> age;
	outfile << name << endl;
	outfile << age;
	outfile.close();
	return 0;
}

#include<iostream>
#include<windows.h>
#include<string>
#include<fstream>
using namespace std;
int main() {
	string str;
	fstream infile;
	infile.open("C:/Users/98207/Desktop/test2.txt", ios::in);
	while (1) {
		if (infile.eof()) {
			break;
		}
		infile >> str;
		cout << str << endl;
	}
	infile.close();
	return 0;
}

#include<iostream>
#include<string>
#include<fstream>
using namespace std;
int main() {
	fstream outfile;
	char name[20];
	int age;
	// 为什么保存格式是dat，因为使用文本格式会按照文本格式解析，最后出来的是乱码
	outfile.open("C:/Users/98207/Desktop/1.dat", ios::trunc | ios::out | ios::binary);
	cin >> name >> age;
	outfile << name << '\t';
	outfile.write((char*)&age, sizeof(age));  // 二进制写
	outfile.close();
	return 0;
}

#include<iostream>
#include<string>
#include<fstream>
using namespace std;
int main() {
	fstream infile;
	char name[20];
	char temp;
	int age;
	infile.open("C:/Users/98207/Desktop/1.dat", ios::in | ios::binary);
	infile >> name;
	infile.read((char*)&temp, sizeof(temp));  // 丢弃制表符
	infile.read((char*)&age, sizeof(age));
	cout << name << '\t' << age << endl;
	infile.close();
	return 0;
}

#include<iostream>
#include<fstream>  //ofstream
#include<sstream>  // stringstream
using namespace std;
int main() {
	stringstream ret;
	ofstream outfile;
	string name;
	int age;
	outfile.open("C:/Users/98207/Desktop/test2.txt", ios::out | ios::trunc);
	while (1) {
		cin >> name >> age;
		if (cin.eof()) {
			break;
		}
		ret << name << "\t\t\t" << age << endl;  // ret会累积
		// outfile << ret.str();
		// ret.clear();
	}
	outfile << ret.str();
	outfile.close();
	return 0;
}

#include<iostream>
#include<fstream>
#include<string>  // getline, string
using namespace std;
int main() {
	fstream infile;
	string str;
	char name[20];
	int age;
	infile.open("C:/Users/98207/Desktop/test2.txt", ios::in);
	while (1) {
		getline(infile, str);
		if (infile.eof()) {
			break;
		}
		sscanf_s(str.c_str(), "%s %d", name, sizeof(name), & age);  // 这里的参数只能是char类型,这里的空格会替换文件的制表符或者空格
		cout << name << "\t\t\t" << age << endl;
	}
	infile.close();
	return 0;
}

#include<iostream>
#include<fstream>
#include<string>
using namespace std;
int main() {
	// ofstream infile;
	ifstream infile;
	string str;
	infile.open("C:/Users/98207/Desktop/1.txt", ios::in);
	infile.seekg(5, ios::beg);  // 从开始位置偏移5个字节
	while (1) {
		getline(infile, str);
		cout << str;
		if (infile.eof()) {
			break;
		}
	}
	infile.close();
	return 0;
}

#include<iostream>
#include<fstream>
#include<string>
using namespace std;
int main() {
	ifstream infile;
	string str;
	infile.open("C:/Users/98207/Desktop/1.txt", ios::in);
	infile.seekg(5, ios::beg);  // 设置偏移量位5个字节
	cout << "文件指针偏移量：" << infile.tellg() << endl;  // 相对于文件起始位置
	infile.close();
	return 0;
}

#include <iostream>
#include <string>
#include <fstream>
using namespace std;
int main() {
	ofstream outfile;
	outfile.open("user1.txt", ios::out | ios::trunc);
	outfile << "123456789";
	outfile.seekp(3, ios::beg);  // 指针先指向开头，然后向后偏移三个字节
	outfile << "ABC";
	outfile.close();
	return 0;
}