TacAndReverse

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct line_t line_t;
struct line_t {
  char *line;
  line_t *next;
};
static void reverse(char *s) {
  char *start, *end, tmp;
  if (!s || !*s) return;
  start = s;
  end = s + strlen(s) - 1;
  while (start < end) {
    tmp = *start;
    *start = *end;
    *end = tmp;
    start++;
    end--;
  }
}
static line_t *new_line(char *line) {
  line_t *new = (line_t *) malloc(sizeof(line_t));
  new->line = (char *) malloc(BUFSIZ);
  strcpy(new->line, line);
  reverse(new->line);
  new->next = NULL;
  return new;
}
static void push(line_t *top, char *line) {
  line_t *new = new_line(line);
  if (!top->next) {
    top->next = new;
    return;
  }
  new->next = top->next;
  top->next = new;
}
static char *pop(line_t *top) {
  char *line;
  if (!top->next) return NULL;
  line = top->next->line;
  top->next = top->next->next;
  return line;
}
int main(const int argc, const char **argv) {
  FILE *in = fopen(argv[1], "r");
  char line[BUFSIZ], *p;
  line_t top;
  top.next = NULL;
  while (fgets(line, BUFSIZ, in)) {
    line[strlen(line) - 1] = '\0';
    push(&top, line);
  }
  while ((p = pop(&top)))
    printf("%s\n", p);
  return 0;
}