/*Напишите программу, которая будет выводить последние N строк входного потока.
Значение N по умолчанию – 10*/
#include <stdio.h>
#include <stdlib.h>

#define MAXLINES        1024
#define MAXINPUT        10240
#define DEF_NUM_LINES   10

int  getlines   (char *);
void parse_args (int, char **);

char  linestr[MAXINPUT];
char *lineptr[MAXLINES];

int num_of_lines = DEF_NUM_LINES;

int main (int argc, char *argv[]) {
        int lines;
        int ltp = 0;
        int i; int c;

        *lineptr = linestr;

        if (argc > 1) {
                parse_args(argc, argv);
        }
        lines = getlines(linestr);

        if (num_of_lines == 0) {
                num_of_lines = 10;
        }

        ltp = lines < num_of_lines ? lines : num_of_lines;
        printf ("\n>>> Printing %d line(s):\n", ltp);
        if (ltp == DEF_NUM_LINES) {
                printf (">>> The default number of lines to print is ");
                printf ("%d\n", DEF_NUM_LINES);
        }
        printf ("\n");

        for (i = lines; i > 0; i--) {
                while ((c = *lineptr[0]++) != '\n') {
                        if (i <= ltp) {
                                printf ("%c", c);
                        }
                }
                if (c == '\n' && i <= ltp) {
                        printf ("\n");
                }
        }

        return 0;
}

int getlines (char *buffer) {
        int i, count = 0;
        char c;

        for (i = 0; (c = getchar()) != EOF && i < MAXINPUT; i++) {
                *buffer++ = c;
                if (c == '\n') {
                        lineptr[++count] = buffer;
                }

        }
        *buffer++ = '\0';

        return count;
}

void parse_args (int argc, char **argv) {
        char c;

        while (--argc > 0 && (*++argv)[0] == '-') {
                c = *++argv[0];
                switch (c) {
                case 'n':
                        num_of_lines = atoi(*(argv + 1));
                        break;
                }
        }
}