Dennis -
    The return value from .C will almost never be useful.  If you want to bring
results from the C environment into R, you need to do it by passing an address 
to
.C which will receive the result.
    You may find this document helpful when interfacing R to C:

         http://www.stat.berkeley.edu/classes/s243/calling.pdf

                                        - Phil Spector
                                         Statistical Computing Facility
                                         Department of Statistics
                                         UC Berkeley
                                         spec...@stat.berkeley.edu


On Sun, 2 Feb 2014, Dennis Fisher wrote:

R 3.0.1
OS X

Colleagues,

I am experimenting with incorporating C code into R.  After compiling the C 
code with:
        R CMD SHLIB -o FILE.so FILE.c
and executing:
        dyn.load(“FILE.so”)
(without any errors), I execute the following R functions in a terminal window:
        READSAS         <- function(sourcefile) .C("readsas", sourcefile)
        OUTPUT          <- READSAS("../SASFILES/sdrug.sas7bdat")
R / C then reads a sas7bdat file and sends the contents to the terminal window.

I expected OUTPUT to contain the text that appear in the terminal window (i.e., 
the contents of the file).  But, that is not the case; OUTPUT contains:
        [[1]]
        [1] "../SASFILES/sdrug.sas7bdat"
It is not clear to my how to capture that appears in the terminal window.

Ultimately, I may need to modify the C code so that the output goes to a file, 
which I then read into R.  However, it would be better if I did not need to 
modify the C code.
Does anyone have any ideas of how I can capture this output within R?

Dennis

Dennis Fisher MD
P < (The "P Less Than" Company)
Phone: 1-866-PLessThan (1-866-753-7784)
Fax: 1-866-PLessThan (1-866-753-7784)
www.PLessThan.com

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