#include <stdio.h>
#include <wctype.h>
int main ()
{
  wchar_t c;
  int i=0;
  wchar_t str[] = L"Example sentence to test iswblank\n";
  while (str[i])
  {
    c = str[i];
    if (iswblank(c)) c = L'\n';
    putwchar (c);
    i++;
  }
  return 0;
}

输出

Ex
ample
sentence
to
test
iswblank