I tried the following example:

```

#+begin_src shell :mkdir yes :dir "data/tmp" :results file :file 
"crackzor_1.0.c.gz"
wget -c "http://ben.akrin.com/crackzor/crackzor_1.0.c.gz"
#+end_src

#+RESULTS:
[[file:data/tmp/crackzor_1.0.c.gz]]
```

But the files is empty, I check out Org-mode document about `:file` 
header argument, seems org-babel will write result to `:file` specified 
file. I wander how I can handle upper case correctly? (don't write 
result to file, just insert a link to downloaded file as a result)