[移动开发]c++一个程序搞懂基本文件读取写入操作

#include<iostream>
#include<string>
#include<fstream>


using namespace std;

void test01()
{
	fstream file("hfj.txt",ios::out);
	file<<"test01"<<123<<endl;
	file.close();
}
void test02()
{
	fstream file;
	file.open("hfj.txt",ios::out);
	file<<"test02"<<endl;
	file.close();
}

void test02e()
{
	fstream file;
	file.open("hfj.txt",ios::out|ios::app);  //app 追加方式写文件
	file<<"test02e"<<endl;
	file.close();
}

void test03()
{
	ofstream file("hfj.txt",ios::app);
	file<<"test03"<<endl;
	file.close();
}

void read01()
{
	fstream file("hfj.txt",ios::in);
	if(!file.is_open()) cerr<<"打开文件失败"<<endl;
	cout<<"******read01*****"<<endl;
	string s;
	file>>s;
	cout<<s<<endl;
	cout<<endl;
	file.close();
}

void read02()
{
	fstream file;
	file.open("hfj.txt",ios::in);
	if(!file.is_open()) cerr<<"打开文件失败"<<endl;
	cout<<"******read02 while(file>>s)*****"<<endl;
	string s;
	while(file>>s){
	cout<<s<<endl;
	}
	cout<<endl;
	file.close();
}
void read02e()
{
	fstream file;
	file.open("hfj.txt",ios::in|ios::ate);  //ate 初始位置文件尾部
	if(!file.is_open()) cerr<<"打开文件失败"<<endl;
	cout<<"******read02e ios::in|ios::ate*****"<<endl;
	string s;
	file.seekg(0);  //重新定位文件起始位置
	while(file>>s){     //>>也是遇到换行就停止
	cout<<s<<endl;
	}
	cout<<endl;
	file.close();
}
void read03()
{
	fstream file("hfj.txt",ios::in);
	if(!file.is_open()) cerr<<"打开文件失败"<<endl;
	cout<<"******read03 while(file.getline(s,sizeof(s)/sizeof(char)))**"<<endl;
	char s[1024];
	while(file.getline(s,sizeof(s)/sizeof(char))){
	cout<<s<<endl;  //一次读取一行，getline默认读取到换行符时结束，输出要手动加\n
	}
	cout<<endl;
	file.close();
}
void read04()
{
	fstream file("hfj.txt",ios::in);
	if(!file.is_open()) cerr<<"打开文件失败"<<endl;
	cout<<"******read04 while((s=file.get())!=EOF)*****"<<endl;
	char s;
	while((s=file.get())!=EOF){
	cout<<s;  //每循环一次读取一个字符，也读取\n，所以输出不用加换行
	}
	cout<<endl;
	file.close();
}
int main()
{
	//*******文件的写入********//
	cout<<"*****文件已经以三种方式写入*****"<<endl;
	cout<<endl;
	test01(); //file("hfj.txt",ios::out)
	test02();  //file.open("hfj.txt",ios::out)
	test02e(); //ios::out|ios::app

	test03();  //ofstream file("hfj.txt",ios::app)

	//*******文件的读取********//
	read01();  //只能读取一行数据
	read02();
	read02e();
	read03();
	read04();

	system("pause");
	return 0;
}