#include <iostream>
#include <fcntl.h>
#include <unistd.h>

using namespace std;

int main(int argc, char * argv[]) {
    if (argc != 3) {
       cerr << "Usage " << argv[0] << " source dest" << endl;
       return 1;
    }

    string sourceFileName{argv[1]};
    string destFileName{argv[2]};

    cout << "Copying from " << sourceFileName << " to " << destFileName << endl;

    int infd{open(sourceFileName.c_str(), O_RDONLY)} ;

    if (infd == -1) {
       string msg = "\tError open " + sourceFileName + " :";
       perror(msg.c_str());
       return -1;
    }

    int flags{O_WRONLY | O_CREAT | O_EXCL};
    int perms{S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH};
    int outfd{open(destFileName.c_str(), flags, perms)};

    if (outfd == -1) {
       string msg = "\tError open " + destFileName + " :";
       perror(msg.c_str());
       return -1;
       close(infd);
    } 
   
    const size_t BLOCK_SIZE{1000};
    size_t actualRead{0};
    char buffer[BLOCK_SIZE];

    while ((actualRead = read(infd, buffer, BLOCK_SIZE)) > 0) {
        if(write(outfd, buffer, actualRead) != actualRead) {
           perror("\tError write: ");
        }
    }

    if (actualRead < 0) {
        perror("\tError read: ");
    }

    close(infd);
    close(outfd);
    return 0;
}