C++中输入输出流及文件流操作总结

#include <iostream>
using namespace std;

int main()
{
 char ch1;
 int look;
 char str1[11] = {0};
 char str2[11] = {0};
 char str3[100] = {0};
 
 //从流中取一个字符，然后在放进去
 ch1 = cin.get();
 cin.putback(ch1);

 //判断流中的第一个字符是不是放进去的那个字符
 look = cin.peek();
 if(look == (int)ch1)
 {
 cout<<"cin.peek()放进去的字符在第一个位置"<<endl;
 }
 else
 {
 cout<<"cin.peek()放进去的字符不是在第一个位置"<<endl;
 }

 //从流中读取10个字符
 cin.get(str1,11);

 //从流中忽略5个字符，再读取10个字符
 cin.ignore(5);
 cin.get(str2,11,EOF);

 //最后读取剩下的字符，最后输出读到的所有字符
 cin.getline(str3,100);

 //输出读到的数据
 cout<<"第一个字符"<<ch1<<endl;
 cout<<"第一组 字符串："<<str1<<endl;
 cout<<"第二组 字符串："<<str2<<endl;
 cout<<"剩下的字符串："<<str3<<endl;

 system("pause");
 return 0;
}

0123456789abcde9876543210zzzzzzzzzzxxxxxxxxxxxxxyyyyyyyyyyyy
cin.peek()放进去的字符在第一个位置
第一个字符0
第一组 字符串：0123456789
第二组 字符串：9876543210
剩下的字符串：zzzzzzzzzzxxxxxxxxxxxxxyyyyyyyyyyyy

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

int main()
{
 char fname[] = "d:/file1.txt";
 char buff[1024]= {0};
 /*********** 写文件 *************/
 //方式1 输出流ofstream对象调用fopen函数
 ofstream fout;
 fout.open(fname,ios::out);
 if(!fout)
 {
 cout<<"打开文件失败"<<fname<<endl;
 }
 fout<< "hello world !"; //通过左移运算符写入字符串
 fout.flush();
 fout.close();

 //方式2 调用输出流ofstream对象的构造函数
 ofstream fout1(fname,ios::out);
 if(!fout1)
 {
 cout<<"打开文件失败"<<fname<<endl;
 }
 fout1.put('h'); //通过put函数写入字符
 fout1.put('e');
 fout1.put('l');
 fout1.put('l');
 fout1.put('o');
 fout1.put('\n');
 fout1.flush();
 fout1.close();

 //文件流对象写文件
 fstream file2(fname,ios::in|ios::out);
 file2<<"abdfd\n";
 file2<<"11111\n";
 file2.flush();
 file2.close();

 /*********** 读文件 *************/
 //输入流ifstream对象读取文件内容
 ifstream fin;
 fin.open(fname,ios::in);
 fin.getline(buff,1024); //通过getline函数读取字符串
 cout<<buff<<endl; 
 fin.close();
 
 //文件流对象读文件内容
 fstream file1(fname,ios::in|ios::out);
 file1>>buff; //通过右移运算符读出字符串
 file1.close();
 cout<<buff<<endl;


 system("pause");
 return 0;
}

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

class Teacher
{
public:
 Teacher()
 {

 }
 Teacher(int age,char name[20])
 {
 this->age = age;
 strcpy(this->name,name);
 }
 void prinfInfo()
 {
 cout<<"Teacher name:"<<this->name<<"  age:"<<this->age<<endl;
 }
private:
 int age;
 char name[20];
};

int main()
{
 Teacher t1(31,"xiaoming");
 Teacher t2(32,"xiaohong");
 Teacher t3(33,"xiaohua");
 Teacher t4(34,"xiaoxin");
 char fname[] = "d:/file2";
 fstream fs(fname,ios::binary|ios::out);
 if(!fs)
 {
 cout<<"文件打开失败"<<endl;
 }
 fs.write((char *)&t1,sizeof(Teacher));
 fs.write((char *)&t2,sizeof(Teacher));
 fs.write((char *)&t3,sizeof(Teacher));
 fs.write((char *)&t4,sizeof(Teacher));
 fs.flush();
 fs.close();

 fstream fs2(fname,ios::binary|ios::in);
 if(!fs)
 {
 cout<<"文件打开失败"<<endl;
 }
 Teacher tt;
 fs2.read((char *)&tt,sizeof(Teacher));
 tt.prinfInfo();
 fs2.read((char *)&tt,sizeof(Teacher));
 tt.prinfInfo();
 fs2.read((char *)&tt,sizeof(Teacher));
 tt.prinfInfo();
 fs2.read((char *)&tt,sizeof(Teacher));
 tt.prinfInfo();
 fs2.close();

 system("pause");
 return 0;
}

Teacher name:xiaoming  age:31
Teacher name:xiaohong  age:32
Teacher name:xiaohua  age:33
Teacher name:xiaoxin  age:34