readline() and Rterm in Windows

Thu, Nov 3, 2005 12:35 AM

I've tried your proposal in a number of ways, and
there must be something I'm not understanding. If I
run your script (using source() in RGui, or ctrl-R
from the R Editor, I get:

Error in file("CONOUT$", "w") : unable to open
connection
In addition: Warning message:
cannot open file 'CONOUT$', reason 'Permission denied'

so I added the path as in:

conout <- file('C:\\R\\R-2.2.0\\CONOUT$','w')
conin <- file('C:\\R\\R-2.2.0\\CONIN$', 'r')
cat('Please enter an ID:', file=conout)
flush(conout)
id <- readLines(conin, 1)
print(id)


Using RGui and ctrl-R from the R Editor, I get

Error in file("C:\\R\\R-2.2.0\\CONIN$", "r") : 
        unable to open connection
In addition: Warning message:
cannot open file 'C:\R\R-2.2.0\CONIN$', reason 'No
such file or directory'

Error in readLines(conin, 1) : object "conin" not
found

and with

Error in file("C:\\R\\R-2.2.0\\CONIN$", "r") : 
        unable to open connection
In addition: Warning message:
cannot open file 'C:\R\R-2.2.0\CONIN$', reason 'No
such file or directory'

When I create a batch file with the following command
:
C:\R\R-2.2.0\bin\Rterm.exe --vanilla
<C:\R\R-2.2.0\foo.R> C:\R\R-2.2.0\foo.out

and double click on the batch file, the out file gives
me:

R : Copyright 2005, The R Foundation for Statistical
Computing
Version 2.2.0  (2005-10-06 r35749)
ISBN 3-900051-07-0
. . .
Type 'q()' to quit R.

and nothing else. In none of the situations do I get
prompted for input. What am I doing hopelessly wrong?

Mikkel

--- Duncan Murdoch <murdoch at stats.uwo.ca> wrote:

Mikkel Grum wrote:

Duncan and Prof, thanks for your comments and
apologies for not being more specific. I'm not

getting

the same results you get from the steps you

propose.

If I write a script foo.R with two lines

	id <- readline("Please enter an ID: ")
	id

and then use source("foo.R") (either at the Rterm
prompt, or in RGui) it is true that get prompted,

but

the second line does not visibly run, i.e. I get

source("id.r")

Please enter an ID: 5


and if I then type id, I get

id

[1] "id"

If I cut and paste the two lines in RGui (in one

go),

I get

id <- readline("Please enter an ID: ")

Please enter an ID: id


What I really want is a batch file on the desktop

with

the following commands:

   c:\r\R-2.2.0\bin\Rterm.exe --no-save

--no-restore

<script.R> script.out 2>&1
   c:\texmf\miktex\bin\latex
\nonstopmode\input{blue.tex}


and script.R reads something like:

   id <- readline("Please enter an ID: ")
   id
   Sweave("blue.Rnw")

I said that script.R didn't run, which was an
incorrect description. It runs without prompting

for

the ID, and gives error messages all through

because

blue.Rnw needs the id.

This is a very simplified version of what I'm

doing,

but if I use only the first line of the batch file

and

the first two lines of the script and could get

that

to work, I could figure out the rest.

It won't work so simply.  You're redirecting stdin,
so user input would 
be taken from there; you're redirecting stdout and
stderr, so the prompt 
won't be visible to the user.

You need to open new handles to the console.  The
code below will do it 
in Windows; the syntax to specify the console in
Unix-alikes will be 
different (but I don't know what it is).

conout <- file('CONOUT$','w')
conin <- file('CONIN$', 'r')
cat('Please enter an ID:', file=conout)
flush(conout)
id <- readLines(conin, 1)
print(id)

Duncan Murdoch

readline() and Rterm in Windows

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