[Rd] readLines function with R >= 3.5.0

[Michael Lawrence]

Hi Jen,

Please provide a reproducible example, since the original stack
overflow example works in both trunk and patched.

Thanks,
Michael

On Tue, Jun 19, 2018 at 3:45 PM, Jennifer Lyon
<jennifer.s.lyon using gmail.com> wrote:
> 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]]
>> >     >>
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>> >
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