Programming

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>

main (int argc, char **argv)
{
    int bytes_read, bytes_written;
    struct stat inode;
    int input_fd, output_fd;
    char buffer[64];
    int eof = 0;
    int i;
       
    /* Check the command line arguments */
    if (argc != 3) 
    {
         printf("syntax is:         %s <fromfile> <tofile>\n", argv[0]);
        exit (1);
    }
  
    /* Check the input file exists and is a file */
    if ((stat(argv[1], &inode) == -1) || (!S_ISREG(inode.st_mode)))
    {
        printf("%s is not a file\n", argv[1]);
        exit(2);
    }
  
    /* Check that the output file doesnt exist */
    if (stat(argv[2], &inode) != -1)
    {
        printf("Warning: The file %s already exists. Not going to overwrite\n", argv[2]);
        exit(2);
    }

    /* Open the input file for reading */
    input_fd = open(argv[1], O_RDONLY, 0);
    if (input_fd == -1)
    {
        printf("%s cannot be opened\n", argv[1]);
        exit(3);
    }
   
    output_fd = open(argv[2], O_CREAT | O_WRONLY | O_EXCL , S_IRUSR|S_IWUSR);
    if (output_fd == -1)
    {
        printf("%s cannot be opened\n", argv[2]);
        exit(3);
    }

    /* Begin processing the input file here */
    while (!eof)
    {
        bytes_read = read(input_fd, buffer, sizeof(buffer));
    
        if (bytes_read == -1)
        {
            printf("%s cannot be read\n", argv[1]);
            exit(4);
        }
    
        if (bytes_read > 0)
        {
            bytes_written = write(output_fd, buffer, bytes_read);
            if (bytes_written == -1)
            {
                printf("There was an error writing to the file %s\n",argv[2]);
                exit(4);
            }

            if (bytes_written != bytes_read)
            {
                printf("Devistating failure! Bytes have either magically appeared and been written or dissapeard and been skipped.  Data is inconsistant!\n");
                exit(101);
            }
        } 
        else
        {
            eof = 1;
        }
    }
      close(input_fd);
    close(output_fd);

}