c++文件复制

#include<iostream>
#include<fstream>
#include<cstring>

using namespace std;

int main(int argc, char* argv[])
{
    using namespace std;
    if (argc < 3){
        cout << "filename missed" << endl;
        return 0;
    }
    ifstream in(argv[1], ios::binary | ios::in);
    if (!in){
        cout << "source file open failed" << endl;
        return 0;
    }
    ofstream out(argv[2], ios::binary | ios::out); //打开文件用于写
    if (!out) {
        cout << "New file open error." << endl;
        in.close(); //打开的文件一定要关闭
        return 0;
    }
    if (strcmp(argv[1], argv[2])==0) {
        cout << "the src file can't be same with dst file" << endl;
        exit(EXIT_FAILURE);
    }
    char buf[2048];
    while (in)
    {
        //read从in流中读取2048字节，放入buf数组中，同时文件指针向后移动2048字节
        //若不足2048字节遇到文件结尾，则以实际提取字节读取。
        in.read(buf, 2048);
        //gcount()用来提取读取的字节数，write将buf中的内容写入out流。
        out.write(buf, in.gcount());
    }
    //char c;
    //while (in.get(c)){
    //    out.put(c);
    //}
    in.close();
    out.close();
}