文件i/o

案例1：写文件，然后读文件

#include <iostream>
using namespace std;
#include "fstream"

int main92()

	char fileName[80];
	char buffer[255];

	cout << "请输入一个文件名: ";
	cin >> fileName;

	ofstream fout(fileName, ios::app);
	fout << "1111111111111111111
";
	fout << "22222222222222222
";
	//cin.ignore(1,‘
‘);
	cin.getline(buffer,255); //从键盘输入
	fout << buffer << "
";
	fout.close();

	ifstream fin(fileName);
	cout << "Here‘s the the content of the file: 
";
	char ch;
	while(fin.get(ch))
		cout << ch;

	cout << "
***End of file contents.***
";
	fin.close();
	system("pause");
	return 0;

#include <fstream> 
usingnamespace std; 

int main()  
 
        ofstream myfile("c:\\1.txt",ios::out|ios::trunc,0); 
        myfile<<"gd_无痕"<<endl<<"网址："<<"https://i.cnblogs.com"; 
        myfile.close() 
        system("pause"); 

#include <iostream> 
#include <fstream> 
usingnamespace std; 
int main()  
 
        ofstream myfile("c:\\1.txt",ios::app,0); 
        if(!myfile)//或者写成myfile.fail() 
         
                cout<<"文件打开失败，目标文件状态可能为只读！"; 
                system("pause"); 
                exit(1); 
         
        myfile<<"gd_无痕"<<endl<<"网址："<<"https://i.cnblogs.com"<<endl; 
　　　　 myfile.close()；

#include <iostream> 
#include <fstream> 
usingnamespace std; 
int main()  
 
        ofstream myfile; 
        myfile.open("c:\\1.txt",ios::out|ios::app,0); 
        if(!myfile)//或者写成myfile.fail() 
         
                cout<<"文件创建失败,磁盘不可写或者文件为只读!"; 
                system("pause"); 
                exit(1); 
        

  　　　 myfile<<"gd_无痕"<<endl<<"网址："<<"https://i.cnblogs.com"; 
        myfile.close() 
        system("pause"); 

#include <iostream> 
#include <fstream> 
#include <string> 
usingnamespace std; 
int main()  
 
        ifstream myfile; 
        myfile.open("c:\\1.txt",ios::in,0); 
        if(!myfile) 
         
                cout<<"文件读错误"; 
                system("pause"); 
                exit(1); 
         
        char ch; 
        string content; 
        while(myfile.get(ch)) 
         
                content+=ch; 
                cout.put(ch);//cout<<ch;这么写也是可以的 
         
        myfile.close(); 
        cout<<content; 
        system("pause"); 

#include <iostream> 
#include <fstream> 
usingnamespace std; 

int main()  
 
        fstream myfile; 
        myfile.open("c:\\1.txt",ios::out|ios::app,0); 
        if(!myfile) 
         
                cout<<"文件写错误,文件属性可能为只读!"<<endl; 
                system("pause"); 
                exit(1); 
         
        myfile<<"gd_无痕"<<endl<<"网址："<<"https://i.cnblogs.com”;   
　　　　 myfile.close(); 

        myfile.open("c:\\1.txt",ios::in,0); 
        if(!myfile) 
         
                cout<<"文件读错误,文件可能丢失!"<<endl; 
                system("pause"); 
                exit(1); 
         
        char ch; 
        while(myfile.get(ch)) 
         
                cout.put(ch); 
         
        myfile.close(); 
        system("pause"); 

案例

int main()

	char fileName[255] = "c:/teacher.dat";
	ofstream fout(fileName,ios::binary);
	if(!fout)
	
		cout << "Unable to open " << fileName << " for writing.
";
		return(1);
	

	Teacher t1(31, "31");
	Teacher t2(32, "32");
	fout.write((char *)&t1,sizeof Teacher);
	fout.write((char *)&t2,sizeof Teacher);
	fout.close();

	cout << "保存对象到二进制文件里成功!" << endl;

	ifstream fin(fileName,ios::binary);
	if(!fin)
	
		cout << "Unable to open " << fileName << " for reading.
";
		return (1);
	
	Teacher tmp(100,"100");

	fin.read((char *)&tmp,sizeof Teacher);
	tmp.printT();
	fin.read((char *)&tmp,sizeof Teacher);
	tmp.printT();
	system("pause");

	return 0;

第一题
Ios类成员函数实现
#include<iostream>
#include<iomanip>
using namespace std;
int main()
	long a=234;
	double b=2345.67890;
	char c[100];
	cout.fill(‘*‘);
	cout.flags(ios_base::left);
	cout.width(12);
	cout<<a<<endl;
	cout.fill(‘*‘);
	cout.flags(ios::right);
	cout.width(12);
	cout<<a<<endl;
	cout.flags(ios.hex);
	cout<<234<<‘	‘;
	cout.flags(ios.dec);
	cout<<234<<‘	‘;
	cout.flags(ios.oct);
	cout<<234<<endl;
	cout.flags(ios::scientific);
	cout<<b<<‘	‘;
	cout.flags(ios::fixed);
	cout<<b<<endl;
	cin.get(c,99);
	cout<<c<<endl;
	return 0;

操作符实现
#include<iostream>
#include<iomanip>
using namespace std;
int main()
	long a=234;
	double b=2345.67890;
	char c[100];
	cout<<setfill(‘*‘);
	cout<<left<<setw(12)<<a<<endl;
	cout<<right<<setw(12)<<a<<endl;
	cout<<hex<<a<<‘	‘<<dec<<a<<‘	‘<<oct<<a<<endl;
	cout<<scientific<<b<<‘	‘<<fixed<<b<<endl;
	return 0;

第二题

#include<iostream>
#include<fstream>
using namespace std;
int main()
	int i=1;
	char c[1000];
	ifstream ifile1("D:\\1.cpp");
	ifstream ifile2("D:\\2.cpp");
	ofstream ofile("D:\\3.cpp");
	while(!ifile1.eof())
		ifile1.getline(c,999);
		ofile<<c<<endl;
	
	while(!ifile2.eof())
		ifile2.getline(c,999);
		ofile<<c<<endl;
	
	ifile1.close();
	ifile2.close();
	ofile.close();
	return 0;

第三题

#include<iostream>
#include<fstream>
using namespace std;
bool isalph(char);
int main()
	ifstream ifile("C:\\daily.doc");
	char text[1000];
	bool inword=false;
	int rows=0,words=0;
	int i;
	while(!ifile.eof())
		ifile.getline(text,999);
		rows++;
		i=0;
		while(text[i]!=0)
			if(!isalph(text[i]))
				inword=false;
			else if(isalph(text[i]) && inword==false)
				words++;
				inword=true;
			
			i++;
		
	
	cout<<"rows= "<<rows<<endl;
	cout<<"words= "<<words<<endl;
	ifile.close ();
	return 0;

bool isalph(char c)
	return ((c>=‘A‘ && c<=‘Z‘) || (c>=‘a‘ && c<=‘z‘));

第四题

#include<iostream>
#include<fstream>
using namespace std;
int main()
	int i=1;
	char c[1000];
	ifstream ifile("D:\\1.cpp");
	ofstream ofile("D:\\2.cpp");
	while(!ifile.eof())
		ofile<<i++<<": ";
		ifile.getline(c,999);
		ofile<<c<<endl;
	
	ifile.close();
	ofile.close();
	return 0;

第五题

#include<iostream>
using namespace std;
int main()
	int i,l;
	for(i=32;i<127;i++)
		cout<<char(i)<<" ";
		l++;
		if(l%10==0)cout<<endl;
	
	cout<<endl;
	return 0;