#define _POSIX_C_SOURCE 200809L

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

int main(int argc, char * argv[]) {
  char c; int start_arg = 1;
  int append_mode = 0;
  int file_failed = 0;

  while((c = getopt(argc, argv, "ai")) != -1) {
    switch(c) {
      case 'a': append_mode = 1; break;
      case 'i': signal(SIGINT, SIG_IGN); break;
    }
  }

  FILE * files[27] = { 0 };

  char * mode = append_mode == 1 ? "a+" : "w+";

  int j = 0;
  for(int i = optind; i < argc && j < 27; i++) {
    files[j++] = fopen(argv[i], mode);
    if(files == NULL) {
      fprintf(stderr, "%s: could not open/create file %s\n", argv[0], argv[i]);
      return 1;
    }
  }

  while((c = getchar()) != EOF) {
    putchar(c);
    for(j = 0; files[j] != 0 && j < 27; j++) {
      if(fputc(c, files[j]) == EOF) {
        file_failed = 1;
      }
    }
  }

  for(j = 0; files[j] != 0 && j < 27; j++) {
    if(fclose(files[j]) == EOF) {
      fprintf(stderr, "%s: failed to close file %s\n", 
              argv[0], argv[j+start_arg]);
    }
  }

  return file_failed == 0 ? 0 : 2;
}