Re: [Rd] on.exit called on loading ?

From: Duncan Murdoch <murdoch_at_stats.uwo.ca>
Date: Thu 18 Jan 2007 - 12:02:12 GMT

On 1/16/2007 5:12 PM, Dirk Eddelbuettel wrote:
> On 16 January 2007 at 16:39, Duncan Murdoch wrote:
> | On 1/16/2007 4:02 PM, Dirk Eddelbuettel wrote:
> | > I just found out that an .onLoad() function such as this stylized one (where
> | > I just renamed some identifiers)
> | >
> | >
> | > .onLoad <- function(lib, pkg) {
> | > require(zoo, quiet=TRUE, warn.conflicts=FALSE)
> | > library.dynam("foolib", pkg, lib )
> | > if (.Platform$OS.type != "windows") {
> | > initSomeServices()
> | > }
> | > if (.Platform$OS.type != "windows") {
> | > on.exit(closeSomeServices())
> | > }
> | > }
> | >
> | > actually triggers a call of 'closeSomeServices()'. I am probably
> | > misunderstanding something here -- but I thought on.exit() would only be
> | > called on, well, exit ?
> |
> | It's the exit from the function, not the exit from the package (which
> | isn't really all that well defined -- do you mean unloading, exit from
> | R, detaching??
>
> Thanks to Robert (off-list), Henrik and Duncan -- I had indeed forgotten /
> confused what on.exit() is for. Works as advertised here, but that wasn't
> what I wanted at the time. Entirely my bad.
>
> | It's not very easy to have something be guaranteed to execute "when
> | you're done". The RODBC package does it using an external pointer,
> | which has a hook that is called when R shuts down. If it's good enough
> | to execute on unloading but skip execution on shutdown, then .onUnload
> | is available.
>
> Yes, I am dealing with a moderately more complicated situation (of
> subscribing to some stateful internal 'services') and had not found
> .onUnload to be as reliable as I had hoped. But that's another issue.

reg.finalizer is probably what you want. Since 2.4.0 it has had an option to be called when R shuts down.

Duncan Murdoch



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