writing binary data from RCurl and postForm

I'm using RCurl with postForm() to post to a URL that responds with a
PDF.  I cannot figure out how to write the resulting PDF data to a
file without corruption.

result = postForm(url, binary=TRUE)

Both this:

capture.output(result, file='/tmp/export.pdf')

and this:

f = file('/tmp/export.pdf', 'wb')
write(result, f)
close(f)

result in a corrupted PDF.

I also tried postForm without binary=TRUE but that halts execution
with an "embedded nul in string" error.

I also tried writeBin() but that complains about my result not being a vector.

I can use curl on the command line and this works fine, but I need to
get this working in R.  Any help would be greatly appreciated.

Thanks.

--
Greg Donald

I think that is because the value returned from postForm has an attribute;
remove it by casting the return to a vector

  fl <- tempfile(fileext=".pdf")
  writeBin(as.vector(postForm(url, binary=TRUE)), fl)


The httr package might also be a good bet

  writeBin(content(POST(url)), fl)