[Rd] --interactive and -f/-e
maechler at lynne.stat.math.ethz.ch
Wed Apr 29 12:20:22 CEST 2015
>>>>> Mick Jordan <mick.jordan at oracle.com>
>>>>> on Tue, 28 Apr 2015 18:11:54 -0700 writes:
> I was surprised by this:
> R --interactive -e 'interactive()'
> bash-3.2$ R -q -e 'interactive()' --interactive
>  FALSE
> as the command options document says that --interactive should force
> " When *R* is run in a terminal (via |Rterm.exe| on Windows), it assumes
> that it is interactive if ‘stdin’ is connected to a (pseudo-)terminal
> and not if ‘stdin’ is redirected to a file or pipe. Command-line options
> --interactive (Unix) and --ess (Windows, |Rterm.exe|) override the
> default assumption"
> But the code in system.c does this:
> R_Interactive = R_Interactive && (force_interactive || isatty(0));
> R_Interactive is set to FALSE in the -e/-f processing, and
> force_interactive is set to TRUE in the --interactive processing, so
> there is no way that it can ever override -e/-f. It seems that
> --interactive can only have an effect for something like a pipe. Is this
> actually the expected behavior?
I did not write the code, but maybe "yes".
It may also seem a bit peculiar that it matters *where* on the
commandline --interactive is given :
R -q -e 'interactive()' --interactive
behaves quite differently from
R --interactive -q -e 'interactive()'
and R -q --interactive -e 'interactive()'
the latter two behaving equally, and indeed just starting R
interactively and not obeying the '-e ..' part(s) at all.
Reading the source shows that -e is really just a short cut for
-f / --file=*, because -e writes to a tempfile and then proceeds
as -f (with the tempfile).
As you mentioned "something like a pipe": '--interactive' does
work fine when R is reading from stdin, not just via a pipe,
$ echo 'interactive(); 1+1' | R --interactive --vanilla -q
> interactive(); 1+1
but of course, e.g., also by explicitly reading a file from stdin :
$ echo 'interactive(); commandArgs()' > /tmp/e1.R
$ R --interactive --vanilla -q < /tmp/e1.R
> interactive(); commandArgs()
$ echo 'x <- 1:7; interactive(); x' > /tmp/e2.R
$ R --interactive --vanilla -q < /tmp/e2.R
> x <- 1:7; interactive(); x
 1 2 3 4 5 6 7
So, in principle it should not seem hard to make --interactive
work for '-e' and '-f' as well, but I don't see quickly how.
Just changing the line in unix/system.c you've mentioned above
is clearly not enough.
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