#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <signal.h>
#include <errno.h>
#include <string.h>

int
tee(int fd)
{
  if(fd == -1)
    {
      fprintf(stderr,"%s\n",strerror(errno));
      return 1;
    }
  char buf[8192];
  int read_bytes = 0;
  while((read_bytes = read(0,buf,8192)) > 0)
    {
      write(fd,buf,read_bytes);
      if(fd != 1)
	write(1,buf,read_bytes);
    }
  return 0;
}

int
main(int argc, char *argv[])
{
  int c;
  int append = 0;
  int ignore_signt = 0;
  int fd = 0;
  int FLAGS = O_WRONLY|O_CREAT; /* yeah, it will overwrite the thing if it
			 * can't read what's in the file, thanks
			 * POSIX! */
  while((c = getopt(argc, argv,"ai")) != -1)
    {
      switch(c)
        {
        case 'a': append = 1; break;
        case 'i': ignore_signt = 1; break;
        }
    }
  if(argc == optind)
    {
      if(ignore_signt)
        signal(SIGINT,SIG_IGN);
      tee(1);
    }
  else
    {
      if(argv[argc-1][0] == '-')
        fd = 1;
      if(append)
	FLAGS = O_RDWR|O_APPEND; /* Remember what I said? */

      fd = open(argv[argc-1],FLAGS);
      if(ignore_signt)
        signal(SIGINT,SIG_IGN);
      if(tee(fd) == 1)
        return -1;
    }
  return 0;
}