UbuntuでのC言語によるファイルコピー機能

#include 
#include <string.h>
#include 
#include 

#include 
#include 
#include 

int main(){
    //open file
    int fd1 = open("./cpy_test1.c",O_RDONLY); 
    int fd2 = open("./cpy_test2.c",O_WRONLY| O_CREAT| O_TRUNC,0777);
    if(fd1 == -1){//error
        perror("open");
        return -1;
    }
    printf("fd1=%d
",fd1);

    if(fd2 == -1){ //error
        perror("open");
        return -1;
    }
    printf("fd2=%d
",fd2);

    //read file
    char buf[512] = {0};
    int rret = read(fd1,buf,sizeof(buf));
    if(rret == -1){//error
        perror("read");
        close(fd1);
        return -1;
    }
    printf("rret=%d
",rret);
    
    //write file
    int wret = write(fd2,buf,sizeof(buf));
    if(wret == -1){ //error
        perror("write");
        close(fd2);
        return -1;
    }
    printf("wret=%d
",wret);

    close(fd1); //     
    close(fd2); //      

    return 0;
}