nonascii.c

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

static void
usage(const char* argv0)
{
  fprintf(stderr,
      "Usage: %s\n"
      "  Passes spans of non-ASCII characters from stdin to stdout, "
      "separated by newlines.\n",
      argv0);
  exit(EXIT_FAILURE);
}

static void
filter()
{
  char    cs[BUFSIZ];
  int     r;
  size_t  i;

  i = 0;
  while ((r = getchar()) != EOF) {
    if (0 == (r & 0x80)) {
      if (i != 0) {
        cs[i] = '\0';
        printf("%s\n", cs);
        i = 0;
      }
    }
    else {
      if (i == BUFSIZ - 1) {
        cs[i] = '\0';
        printf("%s", cs);
        i = 0;
      }
      cs[i++] = (char)r;
    }
  }
  if (i != 0) {
    cs[i] = '\0';
    printf("%s\n", cs);
  }
}

int
main(int argc, char* argv[])
{
  if (argc > 1) {
    usage(*argv);
  }
  else filter();
  return 0;
}