Function wc

src/wc.c:371–693

Count words. FILE_X is the name of the file (or null for standard input) that is open on descriptor FD. *FSTATUS is its status. Return true if successful. */

   input) that is open on descriptor FD.  *FSTATUS is its status.
   Return true if successful.  */
static bool
wc (int fd, char const *file_x, struct fstatus *fstatus)
{
  int err = 0;
  char buf[IO_BUFSIZE + 1];
  intmax_t lines, words, chars, bytes, linelength;
  bool count_bytes, count_chars, count_complicated;
  char const *file = file_x ? file_x : _("standard input");

  lines = words = chars = bytes = linelength = 0;

  /* If in the current locale, chars are equivalent to bytes, we prefer
     counting bytes, because that's easier.  */
  if (MB_CUR_MAX > 1)
    {
      count_bytes = print_bytes;
      count_chars = print_chars;
    }
  else
    {
      count_bytes = print_bytes || print_chars;
      count_chars = false;
    }
  count_complicated = print_words || print_linelength;

  /* Advise the kernel of our access pattern only if we will read().  */
  if (!count_bytes || count_chars || print_lines || count_complicated)
    fdadvise (fd, 0, 0, FADVISE_SEQUENTIAL);

  /* When counting only bytes, save some line- and word-counting
     overhead.  If FD is a 'regular' Unix file, using lseek is enough
     to get its 'size' in bytes.  Otherwise, read blocks of IO_BUFSIZE
     bytes at a time until EOF.  Note that the 'size' (number of bytes)
     that wc reports is smaller than stats.st_size when the file is not
     positioned at its beginning.  That's why the lseek calls below are
     necessary.  For example the command
     '(dd ibs=99k skip=1 count=0; ./wc -c) < /etc/group'
     should make wc report '0' bytes.  */

  if (count_bytes && !count_chars && !print_lines && !count_complicated)
    {
      bool skip_read = false;

      if (0 < fstatus->failed)
        fstatus->failed = fstat (fd, &fstatus->st);

      /* For sized files, seek to one st_blksize before EOF rather than to EOF.
         This works better for files in proc-like file systems where
         the size is only approximate.  */
      if (! fstatus->failed && usable_st_size (&fstatus->st)
          && 0 <= fstatus->st.st_size)
        {
          off_t end_pos = fstatus->st.st_size;
          off_t current_pos = lseek (fd, 0, SEEK_CUR);
          if (current_pos < 0)
            ;
          else if (end_pos % page_size)
            {