电商专业学习嵌入式软件开发第六十三天

• C++第九天

今天是C++的最后一天了，下周讲数据库,讲完数据库再讲完qt，我们的课程就完成了,数据库和qt是我比较感兴趣的,毕竟没有代码那么枯燥，但是因为没有打好基础,决定下周再到新班重新学一遍C基础,最起码要能够自己写出来一个项目。今天主要讲文件操作,然后就开始讲项目,老师带着我们迅速过了一个项目,然后又留了一个项目让我们完成,老师说这个和第一个项目类似,所以两天时间够了，我想大部分同学的时间肯定够了,而我就要到下个班重修了。

由iostream生成fstream,istream生成ifstream,ostream生成ofstream

#include 
#include 
using namespace std;

int main(void)
{
    ofstream ofile;
    //默认以写的方式打开文件,若文件不存在,则自动创建文件
    ofile.open("test.data");
    if (ofile.is_open())
    {
        cout << "open ok\n";
        ofile << "Hello World\n" << 88888 << ' ' << 3.14567 << endl;
    }
    else
    {
        cout << "open failed\n";
    }

    return 0;
}

#include 
#include 
#include 
#include 
#include 
using namespace std;

class Student
{
public:
    Student(){}
    Student(const char *name, float score=0)
    {
        strcpy(m_caName, name);
        m_fScore = score;
    }
    const char *getName()
    {
        return m_caName;
    }
    float getScore()
    {
        return m_fScore;
    }
    friend ofstream &operator<< (ofstream &file, const Student &stu);
friend ifstream &operator>> (ifstream &file, Student &stu);
private:
    char m_caName[32];
    float m_fScore;
};

ofstream &operator<< (ofstream &file, const Student &stu)
{
    file << stu.m_caName << ' ' << stu.m_fScore << endl;    
    return file;
}
ifstream &operator>> (ifstream &file, Student &stu)
{
    file >> stu.m_caName >> stu.m_fScore;   
    return file;
}
int main(void)
{
    ofstream ofile;
    ofile.open("stu.info");
//  ofstream ofile("stu.info");//ofstream自带open函数,相当于上面两行
    if (ofile.is_open())
    {
        cout << "open ok\n";
        Student stu("张三三", 89);
        ofile << stu << endl;
    }
    else
    {
        cout << "open failed\n";
    }

    return 0;
}

#include 
#include 
#include 
#include 
#include 
using namespace std;
class Student
{
public:
    Student(){}
    Student(const char *name, float score=0)
    {
        strcpy(m_caName, name);
        m_fScore = score;
    }
    const char *getName()
    {
        return m_caName;
    }
    float getScore()
    {
        return m_fScore;
    }
    friend ofstream &operator<< (ofstream &file, const Student &stu);
friend ifstream &operator>> (ifstream &file, Student &stu);
private:
    char m_caName[32];
    float m_fScore;
};

ofstream &operator<< (ofstream &file, const Student &stu)
{
    file << stu.m_caName << ' ' << stu.m_fScore << endl;    
    return file;
}
ifstream &operator>> (ifstream &file, Student &stu)
{
    file >> stu.m_caName >> stu.m_fScore;   
    return file;
}
int main(void)
{
    ofstream ofile;
    ofile.open("stu.info");//以二进制形式读写文件
    if (ofile.is_open())
    {
        cout << "open ok\n";
        Student stu("张三", 99);
        ofile.write((char *)&stu, sizeof(stu));
        ofile.seekg(0, );//写文件
        Student stu2;
        ofile.read((char*)&stu2, sizeof(stu2));
        cout << stu2.getName << ' ' << stu2.getScore()<< endl;
    }
    else
    {
        cout << "open failed\n";
    }

    return 0;
}

#include 
#include 
#include 
#include 
#include 
using namespace std;

class Student
{
public:
    Student(){}
    Student(const char *name,float score = 0)
    {
        strcpy(m_caName,name);
        m_fScore = score;
    }
    const char *getName()
    {
        return m_caName;    
    }
    float getScore()
    {
        return m_fScore;
    }
    friend ofstream &operator << (ofstream &file,const Student &stu);
    friend ifstream &operator >> (ifstream &file,Student &stu);
private:
    char m_caName[32];
    float m_fScore;
};
ofstream &operator << (ofstream &file,const Student &stu)
{
    file << stu.m_caName << ' ' << stu.m_fScore << endl;
    return file;
}
ifstream &operator >> (ifstream &file,Student &stu)
{
    file >> stu.m_caName >> stu.m_fScore;
    return file;
}
int main(int argc,char *argv[])
{
    ofstream ofile;
    ofile.open("stu.info");//以二进制形式读写文件
    if(ofile.is_open())
    {
        cout << "open ok\n";
        Student stu("zhangsan",99);
        ofile.write((char *)&stu, sizeof(stu));
    
//      ofile.seekp();//写文件

        ofile.close();
        ifstream ifile("stu.info");
        Student stu2;

//      ifile.seekp();//读文件

        ifile.read((char *)&stu2,sizeof(stu2));
        ifile.close();
        cout << stu2.getName() << ' ' << stu2.getScore() << endl;
    }
    else
    {
        cout << "open failed\n";
    }
    return 0;
}

#include 
#include 
#include 
#include 
#include 
using namespace std;

class Student
{
public:
    Student(){}
    Student(const char *name,float score = 0)
    {
        strcpy(m_caName,name);
        m_fScore = score;
    }
    const char *getName()
    {
        return m_caName;    
    }
    float getScore()
    {
        return m_fScore;
    }
    friend ofstream &operator << (ofstream &file,const Student &stu);
    friend ifstream &operator >> (ifstream &file,Student &stu);
private:
    char m_caName[32];
    float m_fScore;
};
ofstream &operator << (ofstream &file,const Student &stu)
{
    file << stu.m_caName << ' ' << stu.m_fScore << endl;
    return file;
}
ifstream &operator >> (ifstream &file,Student &stu)
{
    file >> stu.m_caName >> stu.m_fScore;
    return file;
}
int main(int argc,char *argv[])
{
    fstream file;
//  file.open("stu.info");//默认以读写方式打开文件会保留文件内容
    file.open("stu.info",ios_base::in|ios_base::out|ios_base::trunc);//以读\写\截断的方式打开文件会清空文件里面内容
    if(file.is_open())
    {
        Student s1("lisi",78);
        file.write((char *)&s1,sizeof(s1));//向文件写数据
        cout << file.tellp() << endl;//tellp文件开始位置

        Student s2;
        file.seekg(0,ios_base::beg);//读数据
        file.read((char *)&s2,sizeof(s2));  
        cout << s2.getName() << ' ' << s2.getScore() << endl;
        file.close();
    
        cout << "open ok\n";
    }
    return 0;
}

#include 
#include 
using namespace std;

int main(void)
{
    ifstream ifile;
    //若文件不存在则不会创建文件
    ifile.open("newdata.info");
    if (ifile.is_open())
    {
        string str;
        int data;
        int data2;
        float data3;
        ifile >> str >> data >> data2 >> data3;
        cout << str << ' ' << data << ' ' << data2 << ' ' << data3 << endl;
        cout << "open ok\n";
    }
    else
    {
        cout << "open failed\n";
    }

    return 0;
}

#include 
#include 
#include 
#include 
#include 
using namespace std;

class Student
{
public:
    Student(){}
    Student(const char *name, float score=0)
    {
        strcpy(m_caName, name);
        m_fScore = score;
    }
    const char *getName()
    {
        return m_caName;
    }
    float getScore()
    {
        return m_fScore;
    }
    friend ofstream &operator<< (ofstream &file, const Student &stu);
friend ifstream &operator>> (ifstream &file, Student &stu);
private:
    char m_caName[32];
    float m_fScore;
};

ofstream &operator<< (ofstream &file, const Student &stu)
{
    file << stu.m_caName << ' ' << stu.m_fScore << endl;    
    return file;
}
ifstream &operator>> (ifstream &file, Student &stu)
{
    file >> stu.m_caName >> stu.m_fScore;   
    return file;
}
int main(void)
{
    ifstream ifile;
    ifile.open("stu.info");
//      ifstream ifile("stu.info");//ifstream自带open函数,相当于上面两行
    if (ifile.is_open())
    {
        cout << "open ok\n";
        Student stu;
        ifile >> stu;
        cout << stu.getName() << ' ' << stu.getScore() << endl;
    }
    else
    {
        cout << "open failed\n";
    }

    return 0;
}

#include 
#include 
#include 
#include 
#include 
using namespace std;

class Student
{
public:
    Student(){}
    Student(const char *name, float score=0)
    {
        strcpy(m_caName, name);
        m_fScore = score;
    }
    const char *getName()
    {
        return m_caName;
    }
    float getScore()
    {
        return m_fScore;
    }
    friend ofstream &operator<< (ofstream &file, const Student &stu);
friend ifstream &operator>> (ifstream &file, Student &stu);
private:
    char m_caName[32];
    float m_fScore;
};

ofstream &operator<< (ofstream &file, const Student &stu)
{
    file << stu.m_caName << ' ' << stu.m_fScore << endl;    
    return file;
}
ifstream &operator>> (ifstream &file, Student &stu)
{
    file >> stu.m_caName >> stu.m_fScore;   
    return file;
}
int main(void)
{
    fstream file;
//  file.open("stu.info");//默认以读写方式打开文件会保留文件内容
    file.open("stu.info", ios_base::in|ios_base::out|ios_base::trunc);//以读\写\截断的方式打开文件会清空文件里面内容
    if (file.is_open())
    {
        Student *pstu = NULL;
        for (int i=0; i< 10; i++)
        {
            pstu = new Student("zhangsan", 60+i);
            file.write((char *)pstu,sizeof(Student));
        }
        Student tmp;
        file.seekg(0, ios_base::beg);
//        while (cin >> data)
        while (file.read((char*)&tmp,sizeof(Student)))
        {
            cout << tmp.getScore() << endl;
        }
//        while (!file.eof())
//        {
//            file.read((char*)&tmp,sizeof(Student));
//            if(!file.eof())
//            cout << tmp.getScore() << endl;
//        }
        file.close();
        cout << "open ok\n";
    }

    return 0;
}

#include 
#include 
#include 
#include 
#include 
using namespace std;

class Student
{
public:
    Student(){}
    Student(const char *name, float score=0)
    {
        strcpy(m_caName, name);
        m_fScore = score;
    }
    const char *getName()
    {
        return m_caName;
    }
    float getScore()
    {
        return m_fScore;
    }
    friend ofstream &operator<< (ofstream &file, const Student &stu);
friend ifstream &operator>> (ifstream &file, Student &stu);
private:
    char m_caName[32];
    float m_fScore;
};

ofstream &operator<< (ofstream &file, const Student &stu)
{
    file << stu.m_caName << ' ' << stu.m_fScore << endl;    
    return file;
}
ifstream &operator>> (ifstream &file, Student &stu)
{
    file >> stu.m_caName >> stu.m_fScore;   
    return file;
}
int main(void)
{
    fstream file;
    file.open("stu.info", ios_base::in|ios_base::out|ios_base::trunc);
    if (file.is_open())
    {
        Student s1("zhangsan", 78);
        file.write((char *)&s1, sizeof(s1));
        cout << file.tellp() << endl;

        Student s2;
        file.seekg(0, ios_base::beg);
        file.read((char *)&s2, sizeof(s2));
        cout << s2.getName()<< ' ' << s2.getScore()<< endl;
        file.close();
        cout << "open ok\n";
    }
    return 0;
}

#include 
#include 
#include 
#include 
#include 
using namespace std;

class Student
{
public:
    Student(){}
    Student(const char *name, float score=0)
    {
        strcpy(m_caName, name);
        m_fScore = score;
    }
    const char *getName()
    {
        return m_caName;
    }
    float getScore()
    {
        return m_fScore;
    }
    friend ofstream &operator<< (ofstream &file, const Student &stu);
friend ifstream &operator>> (ifstream &file, Student &stu);
private:
    char m_caName[32];
    float m_fScore;
};
ofstream &operator<< (ofstream &file, const Student &stu)
{
    file << stu.m_caName << ' ' << stu.m_fScore << endl;    
    return file;
}
ifstream &operator>> (ifstream &file, Student &stu)
{
    file >> stu.m_caName >> stu.m_fScore;   
    return file;
}
int main(void)
{
    ofstream ofile;
    ofile.open("stu.info");
    if (ofile.is_open())
    {
        cout << "open ok\n";
        Student stu("张三", 99);
        ofile.write((char *)&stu, sizeof(stu));
//        ofile.seekp();

        ofile.close();
        ifstream ifile("stu.info");
        Student stu2;
//        ifile.seekg();
        ifile.read((char*)&stu2, sizeof(stu2));
        ifile.close();
        cout << stu2.getName()<< ' ' << stu2.getScore()<< endl;
    }
    else
    {
        cout << "open failed\n";
    }

    return 0;
}