Thus, also shell redirection -- which makes heavy use of dup2() --  is handled
correctly:

    $ cachestats /tmp/foo
    open: No such file or directory
    $ nocache sh -c 'echo foo > /tmp/foo'
    $ cachestats /tmp/foo
    pages in cache: 0/1 (0.0%)  [filesize=0.0K, pagesize=4K]