seek()和tell()在文件里转移

#include <iostream>
#include <fstream>
/* run this program using the console pauser or add your own getch, system("pause") or input loop */

int main(int argc, char** argv) 
{
    std::ofstream fout("text.out");
    if(!fout)
    {
        std::cerr << "Error openging the text.out for writing" << std::endl;
    }
    
    fout << "12345";
    std::ios_base::streampos curPos = fout.tellp();
    if(curPos == 5)
    {
        std::cout << "curPos is 5" << std::endl;
    }else
    {
        std::cout << "curPos is not 5" << std::endl;
    }
    
    fout.seekp(2,std::ios_base::beg);
    fout << 0;
    fout.close();
    
    //text.out is 12045
    
    std::ifstream fin("text.out");
    if(!fin)
    {
        std::cerr << "Error openging the text.out for reading" << std::endl;
        return 1;
    }
     
    int textVal;
    fin >> textVal;
    std::cout << textVal << std::endl;
    
    return 0;
}