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Determining the exit code of an "almost finished" R script

4 messages · Gergely Daróczi, Duncan Murdoch

Original
Gergely Daróczi
# 
Dear All,

I'm using "reg.finalizer" in a function that is to be called in R scripts
to do some cleanup on success. I have not found a way to run the function
only if the script run without errors, so when the exit code is expected to
be 0.

What I've tried is checking "geterrmessage()", but unfortunately it's not
perfect: if an error was handled with eg "tryCatch" previously, that
message still shows up there.

Is there any better way of figuring out in "reg.finalizer" or ".Last" if
the session run OK or exiting with !0 exit code?

Thanks,
Gergely
Duncan Murdoch
#
On 08/06/2019 7:42 a.m., Gergely Dar?czi wrote:
Can't you just put the line to run it as the last line of your script? 
You won't get there if there was an error.

The point of reg.finalizer is to run code even if there was an error; 
your situation is much simpler.

Duncan Murdoch
Gergely Daróczi
#
On Sat, Jun 8, 2019 at 2:13 PM Duncan Murdoch <murdoch.duncan at gmail.com> wrote:
Thank you very much, Duncan, but unfortunately, that's not feasible.

"reg.finalizer" is called from a function early in the script, which
function first checks when the same script last run and optionally
exists early.
If that optional early exit (within the helper function) doesn't
happen, then the "reg.finalizer" call sets a status update when the R
script has finished, but that should only happen if the script run
without any problems.

Of course, this helper could be split into two -- (1) function call at
the beginning of the script and (2) another at the end, but it would
be much less elegant and error-prone.

I know I'm trying to hack-in some features in my R scripts that should
be better handled by an external job scheduler, but I hope this is
doable.
Duncan Murdoch
#
On 08/06/2019 9:55 a.m., Gergely Dar?czi wrote:
I still think you're using reg.finalizer() in a way it's not designed to 
work, and this makes it more complicated than necessary.  The strategy 
of splitting into two seems safer to me:  you never know when a 
finalizer will be called, because it is triggered by garbage 
collections, and those can happen asynchronously, not under your control.

It is nice to have all code for some purpose in one place, so if you 
really want that, you could put together your own explicitly called 
finalizer, something like this:

   finalizers <- list()

   addFinalizer <- function(fn) {
     finalizers <<- c(finalizers, list(fn))
   }

   runFinalizers <- function() {
     for (i in rev(seq_along(finalizers))) { # Run in reverse order
       finalizers[[i]]()       # Call the finalizer
       finalizers[[i]] <- NULL # Allow related objects to be released
     }
   }


In the place you now call reg.finalizer(), you call addFinalizer() 
instead; so all code specific to that task remains local.  At the end of 
your script if things have been successful, you call runFinalizers().

Duncan Murdoch