Flushing the R output buffer.

Hi David,

thats interesting, I'll keep it in mind for the future.

The solution I came up with involved using PHP to attach a script string
to the end of the command line that starts up R like:

$R_script = "R --silent --slave 2>&1 << 'END'" . $R_script;
$R_script .= "quit()\n";
$R_script .= "END\n";
$file_pointer = popen($R_script. "r");
$R_script_result = "";
while(!feop($file_pointer))
{
    $R_script_result .= fread($file_pointer, 1024);
}
pclose($file_pointer);
The script string was then massaged to extract the values I needed.
In my case I used R to format a string that was a PHP script,
extracted this from $R_script_result  and performed a PHP eval on it
so I did not have to do any complex parsing stuff.

Hopes this helps you some time.

Regards from Richard

Richard,

I run into this problem when trying to control R from a Java program.
Hopefully my solution can help you.

After poking around the source code, I realized that when R starts up, it
choose between interactive or non-interactive mode, based on whether there is
a controlling TTY.  Specifically, line 237 of src/unix/system.c has the line
"R_Interactive = isatty(0);"  My solution is to insert the following line
immediately after line 237:
"if ( getenv("R_FORCE_INTERACTIVE") != NULL ) R_Interactive = TRUE;"
I then compile R.  (You implied that you were adverse to learning how to
compile from source, but it really isn't hard.  See "R Installation and
Administration" documentation from the R webpage.)
Then, within Java, I set the environment variable "R_FORCE_INTERACTIVE" to
"true" and launch R.  I can then write commands to R and read the response,
all without buffering or flushing issues.

I hope this helps.  I would be interest in knowing how well this works for you
or what other solution you come up with.

- - David Dahl

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