C++语言基础 例程 文本文件的读写

贺老师的教学链接  本课讲解

示例：将数据写入ASCII文件

#include <iostream>#include <fstream>#include <cstdlib>using namespace std;int main( ){    int a[10];    ofstream outfile("f1.dat",ios::out);//定义文件流对象，打开磁盘文件"f1.dat"    if(!outfile)                        //如果打开失败，outfile返回0值    {        cerr<<"open error!"<<endl;        exit(1);    }    cout<<"enter 10 integer numbers:"<<endl;    for(int i=0; i<10; i++) //向磁盘文件"f1.dat"输出数据    {        cin>>a[i];        outfile<<a[i]<<" ";    }    cout<<"The numbers have been writen to file. "<<endl;    outfile.close();       //关闭磁盘文件"f1.dat"    return 0;}

示例：从ASCII文件读入数据

#include <iostream>#include <fstream>#include <cstdlib>using namespace std;int main( ){    int a[10],max,i,order;    ifstream infile("f1.dat",ios::in);    //定义输入文件流对象，以输入方式打开磁盘文件f1.dat    if(!infile)    {        cerr<<"open error!"<<endl;        exit(1);    }    for(i=0; i<10; i++)    {        infile>>a[i];  //从磁盘文件读入10个整数，顺序存放在a数组中        cout<<a[i]<<" ";    }          //在显示器上顺序显示10个数    cout<<endl;    max=a[0];    order=0;    for(i=1; i<10; i++)        if(a[i]>max)        {            max=a[i];                //将当前最大值放在max中            order=i;                 //将当前最大值的元素序号放在order中        }    cout<<"max="<<max<<endl<<"order="<<order<<endl;    infile.close();    return 0;}

示例：读写ASCII文件

#include<iostream>#include <fstream>#include <cstdlib>using namespace std;void save_to_file( );void get_from_file();int main( ){    save_to_file( );    get_from_file( );    return 0;}void save_to_file( ){    ofstream outfile("f2.dat");    if(!outfile)    {        cerr<<"open f2.dat error!"<<endl;        exit(1);    }    char c[80];    cin.getline(c,80);    for(int i=0; c[i]!=0; i++)         if(c[i]>='a' && c[i]<='z')            outfile.put(c[i]);        outfile.close(); }void get_from_file(){    char ch;    ifstream infile("f2.dat",ios::in);    if(!infile)    {        cerr<<"open f2.dat error!"<<endl;        exit(1);    }    ofstream outfile("f3.dat");    if(!outfile)    {        cerr<<"open f3.dat error!"<<endl;        exit(1);    }    while(infile.get(ch))        outfile.put(ch-32);         infile.close( );         outfile.close();  }

示例：在显示器上输出文件

#include <iostream>#include <fstream>#include <cstdlib>using namespace std;void display_file(char *filename);int main( ){    display_file("f3.dat");    return 0;}void display_file(char *filename){    ifstream infile(filename,ios::in);    if(!infile)    {        cerr<<"open error!"<<endl;        exit(1);    }    char ch;    while(infile.get(ch))        cout.put(ch);    cout<<endl;    infile.close();}