[R] writing binary data from RCurl and postForm

[Martin Morgan]

On 08/05/2015 11:52 AM, Greg Donald wrote:
> 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 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)

>
> 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
>
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>


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