读写&复制实例

下面的 C++ 程序以读写模式打开一个文件。

file_wr() 在向文件 test.txt 写入用户输入的信息之后，程序从文件读取信息，并将其输出到屏幕上;

file_copy()将文件test.txt里的数据读取出来后，再写入test_1.txt中。

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

//向文件内部写入数据，并将数据读出
void file_wr(void)
{
    char data[100];
    //向文件写入数据
    ofstream outfile;
    outfile.open("test.txt");
    cout << "Write to the file" << endl;
    cout << "Enter your name:" << endl;
    cin.getline(data, 100);
    outfile << data << endl;
    cout << "Enter your age:" << endl;
    cin >> data;
    cin.ignore();
    outfile << data << endl;
    outfile.close();
    //从文件读取数据
    ifstream infile;
    infile.open("test.txt");
    cout << "Read from the file" << endl;
    infile >> data;
    cout << data << endl;
    infile >> data;
    cout << data << endl;
    infile.close();
}


//将数据从一文件复制到另一文件中
void file_copy(void)
{
    char data[100];
    ifstream infile;
    ofstream outfile;
    infile.open("test.txt");
    outfile.open("test_1.txt");
    cout << "copy from test.txt to test_1.txt" << endl;
    while (!infile.eof())
    {
        infile >> data;
        cout << data << endl;
        outfile << data << endl;
    }
    infile.close();
    outfile.close();
}

//测试上述读写文件，与文件数据复制
int _tmain(int argc, _TCHAR* argv[])
{
    file_wr();
    file_copy();
    return 0;
}

当上面的代码被编译和执行时，它会产生下列输入和输出：

$./a.out
Writing to the file
Enter your name: 
John
Enter your age:
20
Reading from the file
John
20
copy from test.txt to test_1.txt
John
20

对于 cin 的操作 使用 getline(cin，str)往往可以实现更加简单以及安全的字符串操作,不同于 cin.getline(char*, int a)，前者可以直接对字符串进行操作。

#include<iostream>
#include<string>
#include<fstream>
using namespace std;
int main()
{
    fstream iofile;
    iofile.open("D:\\t.txt", ios::out | ios::in | ios::trunc);
    string bookname;
    string bookwriter;
    cout << "input the bookname:" << endl;
    getline(cin, bookname);
    iofile << bookname << endl;
    cout << "input the bookwriter:" << endl;
    getline(cin, bookwriter);
    iofile << bookwriter << endl;
    iofile.close();
    cout << "read the input file:" << endl;
    iofile.open("D:\\t.txt");
    while (getline(iofile, bookname))
    {
        cout << bookname << endl;

    }
 
    system("pause");
    return 0;

}

程序输入输出结果：

input the bookname:
we are the world
input the bookwriter:
Tanks
read the input file:
we are the world
Tanks
请按任意键继续. . .