c++ 读写文件

读写文件

#include <fstream>
#include <iostream>
#include <string>
#include <unistd.h> //使用access和F_OK
int main()
{
    //读文件
    std::string ifile_name= "test.txt";
    if (access(ifile_name.c_str(), F_OK) == -1) //判断文件是否存在
    {
        std::cout << "file not exists: " << ifile_name << std::endl;
    }
    else
    {
        std::ifstream infile(ifile_name, std::ios::in); //打开读文件, 使用ifstream
        std::string line;
        while(std::getline(infile, line)) //获取每一行内容, 放到变量line中.
        {
            std::cout << line << std::endl;
        }
        infile.close(); //关闭文件
    }


    //写文件
    std::string ofile_name= "test.txt.out";
    std::ofstream outfile;
    outfile.open(ofile_name); //打开写文件, 使用ofstream
    outfile << "line0" << std::endl; //写入内容
    outfile << "line1" << std::endl;
    outfile << "line2" << std::endl;
    outfile.close(); //关闭

    return 0;
}