[Rd] last user argument missing from Rscript --verbose

[Martin Maechler]

>>>>> Harris A Jaffee <hj at jhu.edu>
>>>>>     on Thu, 18 Sep 2014 19:32:29 +0200 writes:

(using  HTML, please don't )

   > The loop that echoes the arguments almost always stops too soon.  It
   > apparently does that to avoid
   > echoing the "--args" (that had been inserted) when there are no user
   > arguments.  However, when there
   > are user arguments, the next element of the 'av' array is the last
   > argument and usually not "--args",
   > although it can be.
   > ?Rscript is a little sketchy:
   >      `--verbose' gives details of what `Rscript' is doing.  Also passed
   >           on to R.
   > What is passed to R is correct, but the diagnostic is not:
   >  $ Rscript --verbose /dev/null 1 2
   >   running
   >   '/path_to_R --slave --no-restore --file=/dev/null --args 1'
   > Fixed (only tested on Mac):
   >  $ Rscript --verbose /dev/null 1 2
   >   running
   >   '/Library/Frameworks/R.framework/Versions/3.1/Resources/bin/R --slave
   > --no-restore --file=/dev/null --args 1 2'

You are right about the problem, also reproducible on Linux.
You mention a 'fix'.
It looks to me that is just

-	for(i = 1; i < ac-1; i++) fprintf(stderr, " %s", av[i]);
+	for(i = 1; i < ac; i++) fprintf(stderr, " %s", av[i]);

in unix/Rscript.c, right ?

BTW: If one use  -e 'commandArgs()'  instead of   /dev/null one
sees that Rscript's "lying" about the last argument is not
helpful anyway :

  Rscript --verbose -e 'commandArgs()'

  running
    '/usr/local64.sfs/app/R/R-3.1.1-inst/bin/R --slave --no-restore -e commandArgs()'

  [1] "/usr/local64.sfs/app/R/R-3.1.1-inst/bin/exec/R"
  [2] "--slave"                                       
  [3] "--no-restore"                                  
  [4] "-e"                                            
  [5] "commandArgs()"                                 
  [6] "--args"                                        

because the '--args' appears anyway and indeed *is* passed to 'R'...

A better fix would rather suppress that; but I will commit the
above change.

Martin Maechler
ETH Zurich