S01_PLIKI_01

/*
Napisz program, który przepisze z istniejącego pliku tekstowego czterdzieści znaków z początku i czterdzieści znaków z końca do nowego pliku.
*/

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

#define READ_FILE_PATHNAME "01.c"
#define NEW_FILE_PATHNAME "01_file"
#define BUFFER_SIZE 40

void rewrite_file(int read_fd, int write_fd)
{
    char buffer[BUFFER_SIZE];
    memset(buffer, '\0', BUFFER_SIZE);

    if(read(read_fd, buffer, BUFFER_SIZE-1) == -1) {
        perror("read");
        exit(EXIT_FAILURE);
    }

    if(write(write_fd, buffer, BUFFER_SIZE-1) == -1) {
        perror("write");
        exit(EXIT_FAILURE);
    }

    if(write(write_fd, "\n\n", 2) == -1) {
        perror("write");
        exit(EXIT_FAILURE);
    }
}

int main(void)
{
    int read_fd, write_fd;

    if((write_fd = open(NEW_FILE_PATHNAME, O_CREAT | O_TRUNC | O_WRONLY, 0600)) == -1) {
        perror("open write");
        return EXIT_FAILURE;
    }

    if((read_fd = open(READ_FILE_PATHNAME, O_RDONLY)) == -1) {
        perror("open read");
        return EXIT_FAILURE;
    }

    rewrite_file(read_fd, write_fd);
    lseek(read_fd, -40, SEEK_END);
    rewrite_file(read_fd, write_fd);

    if(close(read_fd) == -1) {
        perror("close read");
        return EXIT_FAILURE;
    }

    if(close(write_fd) == -1) {
        perror("close write");
        return EXIT_FAILURE;
    }

    return EXIT_SUCCESS;
}