[Rd] readLines function with R >= 3.5.0

[Gábor Csárdi]

stdin() is not the same as file("stdin"), see the note in ?stdin.

Gabor

On Mon, 28 May 2018, 10:41 Martin Maechler, <maechler using stat.math.ethz.ch>
wrote:

> >>>>> 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
>
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