Write a C program that makes a copy of a file using standard I/O, and system calls

#include <stdio.h>
#include <stdlib.h>

#include <fcntl.h>
#include <errno.h>
#include <sys/types.h>
#include <unistd.h>

#define BUF_SIZE 8192

int main(int argc, char* argv[]) {

    int input_fd, output_fd;    /* Input and output file descriptors */
    ssize_t ret_in, ret_out;    /* Number of bytes returned by read() and write() */
    char buffer[BUF_SIZE];      /* Character buffer */

/* Are src and dest file name arguments missing */

    if(argc != 3){
        printf ("Usage: cp file1 file2");
        return 1;
    }

    /* Create input file descriptor */
    input_fd = open (argv [1], O_RDONLY);
    if (input_fd == -1) {
            perror ("open");
            return 2;
    }

    /* Create output file descriptor */
    output_fd = open(argv[2], O_WRONLY | O_CREAT, 0644);
    if(output_fd == -1){
        perror("open");
        return 3;
    }

    /* Copy process */
    while((ret_in = read (input_fd, &buffer, BUF_SIZE)) > 0){
            ret_out = write (output_fd, &buffer, (ssize_t) ret_in);
            if(ret_out != ret_in){
                /* Write error */
                perror("write");
                return 4;
            }
    }

    /* Close file descriptors */
    close (input_fd);
    close (output_fd);

    return (EXIT_SUCCESS);
}




Output :    

user@ITDS07:~$ cc Prog1.c
                user@ITDS07:~$ ./a.out source_file.txt destination_file.txt