I am not sure if `pipe()` works for this, but if it turns out that it
does not, then you can use the processx package, e.g.:
> p <- processx::process$new("sed", c("-l", "s/a/x/g"), stdin = "|", stdout =
> "|")
> p$write_input("foobar\n")
> p$read_output()
[1] "foobxr\n"
The `-l` sed flag is to make sed line-buffered, otherwise it is will
not produce output until there is enough.
`$write_input()` and `$read_output()` are not easy to program, in particular:
* `$write_input()` returns the chunk of data that it hasn't managed to
write into the pipe. You need to call `$write_input() again, with this
data next, usually.
* `$read_output()` returns an empty string if there is no data to
read, so typically you want to call `p$poll()` first, to make sure
that there is something to read.
* `$read_output()` might not read whole lines, so maybe
`$read_output_lines()` is better for you.
* Close the stdin of the process if you want to quit cleanly:
`close(p$get_input_connection())`.
* There is currently no way to poll the input side of the pipe. :(
HTH, Gabor
On Mon, Mar 16, 2020 at 11:31 AM Greg Minshall <minsh...@umich.edu> wrote:
>
> hi. i'd like to instantiate sed(1), send it some input, and retrieve
> its output, all via pipes (rather than an intermediate file).
>
> my sense from pipe and looking at the sources (sys-unix.c) is that is
> not possible. is that true? are there any thoughts of providing such a
> facility?
>
> cheers, Greg
>
> ______________________________________________
> R-devel@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
______________________________________________
R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel
