[R-pkg-devel] Calling R's tempdir() from C

Rodrigo Tobar rtob@r @ending from icr@r@org
Fri Aug 10 06:01:45 CEST 2018

Dear all,

I want to create a temporary directory from within my C++ R extension. 
On the other hand, CRAN's policy dictates that one cannot write anything 
outside the boundaries of the session's temporary directory, so I need 
to create it exactly there.

The R API offers R_tmpnam and R_tmpnam2, both of which require the path 
of the directory where the new name will reside. This can be obtained 
using tempdir() in R, but I couldn't find anything similar in the R API. 
Am I missing anything too obvious?

I tried out giving a NULL dirname to R_tmpnam{,2}, hoping that even 
though it's not mentioned in the docs, they would internally use the 
session's tmp dir, but this simply crashed. When embedding R one could 
also use the R_TempDir global variable, but this is flagged as 
unofficial R API for extensions. Finally, the only solution I could find 
was to call the tempdir() R function from within my C++ extension. This 
works fine, but it bothers me that there not an equivalent entry point 
in R's API.

Any pointers would be appreciated. If I'm deeply misunderstanding 
something please also shoot.



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