Dirk,
> Octave had this already in the 1990s, see documentation for 'popen2' here:
thanks. unix that had since the 1970s... :)
cheers, Greg
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Simon,
> FWIW if you're on unix, you can use named pipes (fifos) for that:
i've always wondered what named pipes actually were. thanks!
cheers, Greg
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Gabor, thanks. yes, managing the two-way communication is always a bit
error-prone, as it depends on the input/output characteristics of the
two ends -- they either match, or deadlock. it's too bad if polling is
always *required* -- i'd think sometimes a programmer would be happy
blocking, though
FWIW if you're on unix, you can use named pipes (fifos) for that:
> system("mkfifo my.output")
> p = pipe("sed -l s:hello:oops: > my.output", "w")
> i = file("my.output", "r", blocking=FALSE, raw=TRUE)
> writeLines("hello!\n", p)
> flush(p)
> readLines(i, 1)
[1] "oops!"
Cheers,
Simon
> On 14/0
Well, if you want blocking, you can poll with an infinite timeout.
This returns if
1) there is output,
2) the process terminates, or
3) you interrupt with CTRL+C / ESC /etc.
and then right after the polling, you can read the output. This still
works if the process has finished already.
Gabor
On
On 13 March 2020 at 20:26, Greg Minshall 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 th
On Fri, 13 Mar 2020 20:26:43 +0300
Greg Minshall wrote:
> 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?
Pipes (including those created by popen(3), which R pipe() uses
internally) are u
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 m
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
