c++ 基于文件的增删改查

来源：互联网发布：中国对外援助数据编辑：程序博客网时间：2024/05/16 12:00
wuzhixiang
#include <iostream>#include <fstream>#include <sstream>#include <string>#include <iomanip>#include <windows.h>#define WIDTH 20#define space setw(WIDTH)#define NEWLINE "\r\n"using namespace std;void write(const char *filename){    ofstream out;    out.open(filename,ios::app);    if(!out.is_open())    {        cout<<"open error"<<endl;        return ;    }    else    {        int id,age;        string name;        cout<<"请输入id、姓名、年龄："<<endl;        cin>>id>>name>>age;        out.fill(' ');        out.setf(ios::left);        out<<space<<id<<space<<name<<space<<age<<NEWLINE;        out.close();        cout<<"添加成功！！"<<endl;    }}void read(const char *filename){    ifstream in;    in.open(filename,ios::in);    if(!in.is_open())    {        cout<<"file open error"<<endl;        return ;    }    else    {        stringstream ss;        char line[100];        cout.setf(ios::left);        cout.fill(' ');        cout<<space<<"id"<<space<<"name"<<space<<"age"<<endl;        while(in.peek()!=EOF)        {            in.getline(line,100);            ss<<line;            int id,age;            string name;            ss>>id>>name>>age;            cout<<space<<id<<space<<name<<space<<age<<endl;            ss.str("");            ss.clear();        }        in.close();    }}void del(const char *filename){    int id;    cout<<"请输入您要删除学生的编号"<<endl;    cin>>id;    ifstream in;    in.open(filename,ios::in);    if(!in.is_open())    {        cout<<"file open error"<<endl;        return ;    }    else    {        string temp;        stringstream ss;        int curId;;        while(in.peek()!=EOF)        {            string line;            getline(in,line);            ss<<line;            ss>>curId;            if(curId!=id)            {                temp += line + NEWLINE;            }            ss.str("");            ss.clear();        }        in.close();        ofstream out;        out.open("G:\\students.txt",ios::out);        if(!out.is_open())        {            cout<<"file open error"<<endl;            return ;        }        else        {            out<<temp;            out.close();            cout<<"删除成功！！"<<endl;        }    }}int search_pos(const char *filename,int id){    ifstream in;    in.open(filename,ios::in|ios::binary);    if(!in.is_open())    {        cout<<"file open error"<<endl;        return -1;    }    else    {        stringstream ss;        while(in.peek()!=EOF)        {            int start = in.tellg();            string line;            getline(in,line);            ss<<line;            int curID;            ss>>curID;            if(curID == id)            {                in.close();                return start;            }            ss.str("");        }        cout<<"对不起您查找的同学信息不存在!"<<endl;        in.close();    }    return -1;}void search(const char *filename){    cout<<"请输入您要查找的学生id："<<endl;    int id;    cin>>id;    int pos = search_pos(filename,id);    string line;    fstream in;    in.open(filename,ios::in|ios::binary);    in.seekg(pos,ios::beg);    getline(in,line);    cout.setf(ios::left);    cout<<space<<"id"<<space<<"name"<<space<<"age"<<endl;    cout<<line<<endl;}void edit(const char *filename){    int id,age;    string name;    cout<<"请输入您要修改的学生id"<<endl;    cin>>id;    cout<<"请输入该学生新的姓名、年龄"<<endl;    cin>>name>>age;    stringstream infoTemp;    infoTemp.fill(' ');    infoTemp.setf(ios::left);    infoTemp<<space<<id<<space<<name<<space<<age;    string newInfo;    getline(infoTemp,newInfo);    fstream file;    file.open(filename,ios::in|ios::out|ios::binary);    if(!file.is_open())    {        cout<<"file open error"<<endl;        return ;    }    else    {        int pos = search_pos(filename,id);        file.seekg(pos,ios::beg);        file<<newInfo;        cout<<"修改后信息为："<<endl;        cout<<newInfo<<endl;        file.close();    }}int main(){    const char *filename = "G:\\students.txt";    while(true)    {        cout<<"--------------------------"<<endl;        cout<<"0、查看全部信息"<<endl;        cout<<"1、新增学生信息"<<endl;        cout<<"2、删除学生信息"<<endl;        cout<<"3、修改学生信息"<<endl;        cout<<"4、查找学生信息"<<endl;        int cmd;        cin>>cmd;        system("cls");        switch(cmd)        {            case 0:read(filename);break;            case 1:write(filename);break;            case 2:del(filename);break;            case 3:edit(filename);break;            case 4:search(filename);break;        }    }    return 0;}
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