[R] Controlling R from Java
Warnes, Gregory R
gregory_r_warnes at groton.pfizer.com
Thu Dec 14 16:20:27 CET 2000
Duncan's reply is the best long term solution, but a simple and quick hack
is to append something like
to the end of each commend. This way, when the command finishes, there is a
nice token ("<DONE>") to grab. (The paste bit is to that you don't match
<DONE> from the command string if it gets echoed for some reason.)
atlas% echo ' ls(); cat(paste("\n<DO","NE>\n",sep="") ) ' | R
R : Copyright 2000, The R Development Core Team
Version 1.1.1 (August 15, 2000)
[Previously saved workspace restored]
> ls(); cat(paste("\n<DO","NE>\n",sep="") )
 "beta.binom" "devs"
 "log.beta.binomial.beta.binomial" "p"
> -----Original Message-----
> From: Marc Grushcow [mailto:Marc.Grushcow at ntt.ca]
> Sent: Tuesday, December 12, 2000 3:38 PM
> To: r-help at stat.math.ethz.ch
> Subject: [R] Controlling R from Java
> I'd like to run R (LINUX) under Java. I can create the
> process and connect to
> stdin and stdout. I can send commands in and get output back.
> I don't know how
> to determine when the output is complete - there is no
> trailing "prompt".
> For example, if I send "ls()\n" what I get back is:
> > ls()
> Each of the above two lines is terminated with a 0x0A. I
> would have expected
> Then I could parse for the "\n> " and know when the output is
> complete. The
> problem with checking for data availability on the input
> stream is that it is
> unreliable. R's output buffer might flush unpredictably
> and/or the task
> switching OS might cause R to stop after one buffer is full
> but before another
> is completed. In any case, it is the usual problem of one
> program trying to
> parse another's output in a time sharing environment.
> I'm sure that this problem has been solved before. Any
> suggestions would be
> mailto:Marc.Grushcow at NTT.ca http://www.NTT.ca
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