Your problem seems to be unfamiliarity with this operating-system-specific
feature. You should be reading the OS documentation (e.g. "man fifo" and
learning how to use the feature in general before using it in R. (Hint:
off-topic here.)
Some words to the wise: Make sure you test with two processes, one for reading,
one for writing (this is not a storage medium, it is an inter-process
communication mechanism). Make sure you define a specific number of lines (e.g.
1) when you read unless you want to wait until the writing process closes the
fifo.
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Sent from my phone. Please excuse my brevity.
Worik R <wor...@gmail.com> wrote:
>Friends
>
>I need to get R reading from a fifo. I want it to block till there is
>some
>data in the fifo, consume what input it gets there, do some thing with
>it
>then loop back and block again.
>
>Very simple. Yes? No.
>
>The example in the documentation works OK..
>
> zz <- fifo("foo-fifo", "w+")
> writeLines("abc", zz)
> print(readLines(zz))
> close(zz)
> unlink("foo-fifo")
>
>But when I tryu my code to *read* and *block*, id does not work.
>
>P <- "Myfoofifo"
>C <- fifo(P, "r", blocking=TRUE)
>
>If Myfoofifo does not exist this has an error:
>
>> C <- fifo(P, "r", blocking=TRUE)
>Error in fifo(P, "r", blocking = TRUE) : cannot open the connection
>In addition: Warning message:
>In fifo(P, "r", blocking = TRUE) : cannot open fifo 'Myfoofifo'
>>
>
>> C <- fifo(P, "w+", blocking=TRUE)
>
>succeeds but a read...
>
>> Z <- readLines(C)
>
>hangs. Writing to Myfoofifo from other programmes, opening closing
>even
>deleting it makes no difference.
>
>I am stuck. I can find no pertinent examples. What can I do?
>
>Worik
>
> [[alternative HTML version deleted]]
>
>______________________________________________
>R-help@r-project.org mailing list
>https://stat.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide
>http://www.R-project.org/posting-guide.html
>and provide commented, minimal, self-contained, reproducible code.
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and provide commented, minimal, self-contained, reproducible code.
