[R] options()$width does not equal actual console width - why?

[Petr Savicky]

On Fri, Nov 26, 2010 at 05:32:54PM +0100, Mark Heckmann wrote:
> I am writing a function that breaks the output if it gets bigger than the available console width.
> I noticed that a right margin always remains. The following code shows that the actual console size
> is always bigger than the one reported by options()$width. What might be the reason?
> (Software: MacOS 10.6, R 2.12)
> 
> > cat(paste(rep(c(1:9, 0), each=10), collapse=""))
> 11111111112222222222333333333344444444445555
> 55555566666666667777777777888888888899999999
> 990000000000
> > options()$width
> [1] 46
> 
> > cat(paste(rep(c(1:9, 0), each=10), collapse=""))
> 11111111112222222222333333333344444444445555555555666666666677777
> 77777888888888899999999990000000000
> > options()$width
> [1] 59

I am not sure, whether the actual console size is always bigger. The
command options(width=n) may set the width to any n between 10 and 10000
independently on the actual console size. The help page ?options says

   Some R consoles automatically change the value when they are resized.

In order to get the actual console size under Linux, one can use
Sys.getenv("COLUMNS"). I do not know, whether this applies also to MasOS.

Petr Savicky.