c++程序与txt之间的交互

与txt之间建立联系：

#include<cstdio>
#include<fstream>
#include<iostream>

using namespace std;
 
int main(){
	
	ofstream OpenFile("test.txt");
	if(OpenFile.fail()){
		cout << "´abcdefg" <<endl;
		exit(0); 
	}
	OpenFile<<"abcdefg";
	OpenFile.close();
	system("pause");
	
	return 0;
}

程序运行结果，目录要找好。

从txt中逐行读取内容：

#include<cstdio>
#include<iostream>
#include<fstream>
#include<cassert>
#include<string>

using namespace std;

int main(){
	
	ifstream infile;
	infile.open("test.txt");
	assert(infile.is_open());
	
	string s;
	while(getline(infile,s)){
		cout << s <<endl;
	}
	
	infile.close();
	
	return 0;
}

运行结果：

逐个字符读入：

#include<cstdio>
#include<iostream>
#include<fstream>
#include<cassert>
#include<string>

using namespace std;

int main(){
	
	ifstream infile;
	infile.open("test.txt");
	assert(infile.is_open());
	
	char c;
	while(!infile.eof()){
		infile >> c;
		cout << c <<endl;
	}
	
	infile.close();
	
	return 0;
}

运行结果：

读入包括回车和空格：

#include<cstdio>
#include<iostream>
#include<fstream>
#include<cassert>

using namespace std;

int main(){
	
	ifstream infile;
	infile.open("test.txt");
	assert(infile.is_open());
	
	char c;
	infile >> noskipws;
	while(!infile.eof()){
		infile >> c;
		cout << c;
	}
	
	infile.close();
	
	return 0;
}

运行结果：

文件读入，并简单计算：

#include<cstdio>
#include<iostream>
#include<fstream>
#include<cassert>
#include<string>

using namespace std;

int main(){
	
	ifstream infile;
	infile.open("test_for_sum.txt");
	assert(infile.is_open());
	
	int c,d;
	while(!infile.eof()){
		infile >> c;
		infile >> d;
	}
	cout << c+d;
	
	infile.close();
	
	return 0;
}

程序运行结果：