From hb@maths.lth.se  Sat Mar  1 03:05:04 2003
From: hb@maths.lth.se (Henrik Bengtsson)
Date: Sat Mar  1 03:05:04 2003
Subject: [Rd] RE: [R] File opening error after 1020 files opened
In-Reply-To: <Pine.LNX.4.44.0302282018010.3805-100000@reclus.nhh.no>
Message-ID: <001801c2df96$d52b5330$7341a8c0@alpha.wehi.edu.au>

Maybe open.connection() should also check if the connection is already
open and given an error or at least a warning if it is. Suggested code
update:

open.connection <- function(con, open="r", blocking=TRUE, ...) {
  if (!inherits(con, "connection"))
    stop("argument is not a connection")
  if (isOpen(con))                                               # NEW
    stop("Trying to open a connection that is already open.")    # NEW
  invisible(.Internal(open(con, open, blocking)))
}

Henrik Bengtsson


> -----Original Message-----
> From: Roger Bivand [mailto:Roger.Bivand@nhh.no] 
> Sent: den 1 mars 2003 06:25
> To: ripley@stats.ox.ac.uk
> Cc: Dirk Eddelbuettel; jonathan_li@agilent.com; hb@maths.lth.se
> Subject: Re: [R] File opening error after 1020 files opened
> 
> 
> On Fri, 28 Feb 2003 ripley@stats.ox.ac.uk wrote:
> 
> > Let's take this off R-help.
> > 
> > I did a quick check that connections are behaving:
> > 
> > for(i in 1:2000) {
> > print(i)
> > zz <- file("foo", "rb")
> > foo <- readLines(zz)
> > close(zz)
> > }
> > 
> > for(i in 1:2000) {
> > print(i)
> > zz <- file(tempfile(), "wb")
> > cat("foobar\n", file=zz)
> > close(zz)
> > }
> > 
> > work for me, several times in a session in both Windows and 
> Linux. I 
> > do know that sometimes under Windows file closing fails, but not 
> > often.
> > 
> > The file-handle limit on RH7.2 seems to 8096, and I used at least 
> > 20000 opens.
> > 
> > However, read.pnm has
> > 
> >     con <- file(file, open = "rb")
> >     open(con, open = "rb")
> > ...
> >     close(con)
> 
> Yes, of course. Revision (pixmap_0.3-2.tar.gz) on incoming, 
> should be on 
> CRAN before long. If needed, I can attach it. Runs 10000 
> read.pnm() now 
> without difficulty. I can't recall why I once thought file() 
> just set a 
> handle and open() actually opened it, wrong assumptions can 
> survive for 
> years!
> 
> Thanks,
> 
> Roger
> 
> > 
> > which opens the connection *twice* and that's creating two file 
> > handles and only closing one.  See ?file.
> > 
> > Brian

[SNIP]



[Rd] RE: [R] File opening error after 1020 files opened
Henrik Bengtsson