[Rd] readLines function with R >= 3.5.0

[Jennifer Lyon]

Hi Michael:

I can confirm Martin's comment. I tested my software with r-devel (r74914)
and it works, while with r-patched (r74914) it does not work (it hangs, as
it did in R 3.5.0). I apologize for it taking so long for me to test this,
but is there any chance this fix could make into R 3.5.1?

Thanks.

Jen.

On Wed, Jun 13, 2018 at 6:24 AM, Michael Lawrence <lawrence.michael using gene.com
> wrote:

> Are you sure it's not available in patched? It's definitely in the
> source since 6/1.
>
> Michael
>
>
> On Wed, Jun 13, 2018 at 2:19 AM, Martin Maechler
> <maechler using stat.math.ethz.ch> wrote:
> >>>>>> Michael Lawrence
> >>>>>>     on Tue, 12 Jun 2018 19:27:49 -0700 writes:
> >
> >     > Hi Jen, This was already resolved for R 3.5.1 by just
> >     > disabling buffering on terminal file connections like stdin.
> >
> > and before R 3.5.1 exists, *and*
> > as the change is also not yet available in R patched (!)
> > this means using a version of
> > "R-devel", e.g. for Windows available from
> >    https://cloud.r-project.org/bin/windows/base/rdevel.html
> >
> > Martin
> >
> >     > Sounds like you might want to be running a web service or
> >     > something instead though.
> >
> >     > Michael
> >
> >     > On Tue, Jun 12, 2018 at 4:46 PM, Jennifer Lyon
> >     > <jennifer.s.lyon using gmail.com> wrote:
> >     >> Hi:
> >     >>
> >     >> I have also just stumbled into this bug. Unfortunately, I
> >     >> can not change the data my program receives from
> >     >> stdin. My code runs in a larger system and stdin is sent
> >     >> to a Docker container running my R code. The protocol is
> >     >> I read a line, readLines("stdin", n=1), do some actions,
> >     >> send output on stdout, and wait for the next set of data.
> >     >> I don't have control over this protocol, so I can't use
> >     >> the ^D workaround.
> >     >>
> >     >> I am open for other workaround suggestions. The single
> >     >> line is actually JSON and can be quite large. If there
> >     >> isn't something else cleaner, I am going to try
> >     >> readChar() in a while loop looking for \n but I'm
> >     >> guessing that would likely be too slow.  I am open to
> >     >> other workaround solutions. For the moment I have
> >     >> reverted back to R 3.4.4.
> >     >>
> >     >> Thanks for any suggestions.
> >     >>
> >     >> Jen.
> >     >>
> >     >>
> >     >>>> >>>>> Martin Maechler >>>>> on Mon, 28 May 2018
> >     >>>> 10:28:01 +0200 writes:
> >     >>>>
> >     >>>> >>>>> Ralf Stubner >>>>> on Fri, 25 May 2018 19:18:58
> >     >>>> +0200 writes:
> >     >>>>
> >     >>>> >> Dear all, I would like to draw you attention to this
> >     >>>> >> question on SO:
> >     >>>> >>
> >     >> https://stackoverflow.com/questions/50372043/readlines-
> function-with-new-version-of-r
> >     >>>>
> >     >>>>
> >     >>>> >> Based on the OP's code I used the script
> >     >>>>
> >     >>>> >> #######################################
> >     >>>> >> create_matrix <- function() { >> cat("Write the
> >     >>>> numbers of vertices: ") >> user_input <-
> >     >>>> readLines("stdin", n=1) >> user_input <-
> >     >>>> as.numeric(user_input) >> print(user_input) >> } >>
> >     >>>> create_matrix()
> >     >>>> >> #######################################
> >     >>>>
> >     >>>> >> and called it with "R -f <filename>" from the
> >     >>>> command line.
> >     >>>>
> >     >>>> >> With 'R version 3.4.4 (2018-03-15) -- "Someone to
> >     >>>> Lean On"' the
> >     >> script
> >     >>>> >> prints the inputed number as expected. With both 'R
> >     >>>> version 3.5.0 >> (2018-04-23) -- "Joy in Playing"' and
> >     >>>> 'R Under development
> >     >> (unstable)
> >     >>>> >> (2018-05-19 r74746) -- "Unsuffered Consequences"'
> >     >>>> the script does
> >     >> not
> >     >>>> >> continue after inputing a number.
> >     >>>>
> >     >>>> > I can confirm.  > It "works" if you additionally (the
> >     >>>> [Enter], i.e., EOL) you also > "send" an EOF -- in Unix
> >     >>>> alikes via <Ctrl>-D
> >     >>>>
> >     >>>> > The same happens if you use 'Rscript <filename>'
> >     >>>>
> >     >>>> > I'm not the expert here, but am close to sure that we
> >     >>>> (R core) > did not intend this change, when fixing
> >     >>>> other somewhat subtle > bugs in Rscript / 'R -f'
> >     >>>>
> >     >>>> > Martin Maechler
> >     >>>>
> >     >>>> The same behavior in regular R , no need for a script
> >     >>>> etc.
> >     >>>>
> >     >>>> > str(readLines("stdin", n=1))
> >     >>>>
> >     >>>> then in addition to the input you need to "give" an EOF
> >     >>>> (Ctrl D) in R
> >     >>> = 3.5.0
> >     >>>>
> >     >>>> Interestingly, everything works fine if you use stdin()
> >     >>>> instead of "stdin" :
> >     >>>>
> >     >>>> > rr <- readLines(stdin(), n=1) foo > rr [1] "foo"
> >     >>>> >
> >     >>>> ----------
> >     >>>>
> >     >>>> So, for now use stdin() which is much clearer than the
> >     >>>> string "stdin" anyway
> >     >>>>
> >     >>>> Martin Maechler
> >     >>
> >     >> [[alternative HTML version deleted]]
> >     >>
> >     >> ______________________________________________
> >     >> R-devel using r-project.org mailing list
> >     >> https://stat.ethz.ch/mailman/listinfo/r-devel
> >
> >     > ______________________________________________
> >     > R-devel using r-project.org mailing list
> >     > https://stat.ethz.ch/mailman/listinfo/r-devel
>

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