Command-line arguments and --interactive
Adam D. I. Kramer wrote:
Hello,
I am interested in passing a command or two to R on the command
line. The desired behavior is for R to run these commands first, and then
begin an interactive session. For example:
$ R -e 'foo <- read.csv("/tmp/foo.csv")'
...which would launch R and execute that command, so when I return from
getting coffee, foo would be loaded.
I know that if I put this command into my .Rprofile, it will execute as
desired, but I'm looking for something a bit more modular.
I have tried the following:
$ echo '10*5' | R
...fails unless I specify --save --no-save or --vanilla. I choose the
latter; R prints 50 and quits...but I do not want it to quit!
$ echo '10*5' | R --interactive
...fails in an interesting way: I get an infinite loop of Save workspace
image? [y/n/c]: Save workspace image? [y/n/c]:, etc. I have to kill R in
another window. This also happens with
$ echo '10*5; scan()' | R --interactive
...even though I'd expect scan() to prompt for input. If I specify
$ echo '10*5; scan()' | R --interactive --vanilla
...then R just prints 50 and quits. Is this a bug with "interactive?" The
description of "Force an interactive session" is not informative enough for
me to have any further guess as to what to do here, but my expectation is
that it would make R not auto-quit.
...perhaps I don't know how to use --interactive properly? Could somebody
point me on the right track? Googling for "R --interactive" is nigh untu
useless. :-\
This behavior is present in R 2.9.2 and 2.10.0.
--interactive tells R that there is a human producing the input stream, so it can ask questions and expect them to be answered. In your experiments with it, your input stream was the pipe holding the output of echo, and R got confused because that pipe wouldn't answer its question. Your problem is that you want an input stream that starts out from your fixed code and then switches to your shell's stdin. I think you can do that on some systems by saving your input to a file then concatenating it to stdin, e.g. something like this: echo '10*5; scan()' >test.R cat test.R - | R --interactive I don't know if there's a way to do this in one line, and I'd expect some oddities. Duncan Murdoch
Many thanks! Cordially, Adam Kramer
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