#define _POSIX_C_SOURCE 200809L

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

int stoi_mini(char * str);

int main(int argc, char *argv[]) {
  FILE * current_input_file;
  int i = 1, j = 0; char c;

  int chars_copy = 10;
  int print_head = 0;

  int error_occurred;

  
  if(argv[i][0] == '-') {
    if(argv[i][1] == 'n') {
      i++;
      chars_copy = stoi_mini(argv[i]);
      i++;
    }
  }

  if(argc - i > 1) {
    print_head = 1;
  }

  for(i; i < argc; i++) {
    if(argv[i][0] == '-' && argv[i][1] == '\0') {
      current_input_file = stdin;
    }
    else {
      current_input_file = fopen(argv[i], "r");
      if(current_input_file == NULL) {
	fprintf(stderr, "%s: %s: No such file or directory\n",
		argv[0], argv[i]);
	error_occurred = 1;
      }
    }
    if(print_head) {
      printf("\n==> %s <==\n", argv[i]);
    }
    j = 0;
    c = ' ';
    while(c != EOF && j < chars_copy) {
      c = fgetc(current_input_file);
      if(c == '\n') {
	j++;
      }
      if(c != EOF) {
	fprintf(stdout, "%c", c);
      }
    }
    if(current_input_file != stdin) {
      fclose(current_input_file);
    }
  }

  if(error_occurred) {
    return 1;
  }
  else {
    return 0;
  }
}

int stoi_mini(char * str) {
  int i, str_int = 0;

  for(i = 0; str[i] != '\0' && str[i] != ','; i++) {
    str_int *= 10;
    switch(str[i]) {
      case '0': str_int += 0; break;
      case '1': str_int += 1; break;
      case '2': str_int += 2; break;
      case '3': str_int += 3; break;
      case '4': str_int += 4; break;
      case '5': str_int += 5; break;
      case '6': str_int += 6; break;
      case '7': str_int += 7; break;
      case '8': str_int += 8; break;
      case '9': str_int += 9; break;
      default: return -1;
    }
  }

  return str_int;
}