I don't think there's a standard way--at least, I couldn't find it when I looked. I ended up rolling my own--see https://github.com/kmsquire/VideoIO.jl/blob/master/src/util.jl.
This functionality should probably be part of readandwrite. Cheers, Kevin On Thursday, June 18, 2015, Miguel Bazdresch <eorli...@gmail.com> wrote: > Is there a way to read the spawned process' STDERR? Gnuplot likes to write > most output to it. I've tried > > readandwrite(`gnuplot 2>&1`) > > but gnuplot interprets 2>&1 as a filename and fails. > > This, however, works: > > readandwrite(`gnuplot` .> "/tmp/gnuplot.err") > > but I'd like to avoid having to create a file. > > Thanks! > > On Wed, Jun 17, 2015 at 1:05 PM, Kevin Squire <kevin.squ...@gmail.com > <javascript:_e(%7B%7D,'cvml','kevin.squ...@gmail.com');>> wrote: > >> `open(cmd, "w")` gives back a tuple. Try using >> >> f, p = open(`gnuplot`,"w") >> write(f, "plot sin(x)") >> >> There was a bit of discussion when this change was made (I couldn't find >> it with a quick search), about this returning a tuple--it's a little >> unintuitive, and could be `fixed` in a few different ways (easiest: >> returning a complex type that can be written to and read from), but it's >> probably been off most people's radar. If you're up for it, why don't you >> open an issue (if one doesn't exist). >> >> Anyway, for your particular application, you probably want `readandwrite`: >> >> help?> readandwrite >> search: readandwrite >> >> Base.readandwrite(command) >> >> Starts running a command asynchronously, and returns a tuple >> (stdout,stdin,process) of the output stream and input stream of the >> process, and the process object itself. >> >> Which *also* returns a tuple (but at least now you know). >> >> See also http://blog.leahhanson.us/running-shell-commands-from-julia.html, >> which has a full rundown of reading and writing from processes. >> >> Cheers! >> Kevin >> >> On Wed, Jun 17, 2015 at 9:03 AM, Miguel Bazdresch <eorli...@gmail.com >> <javascript:_e(%7B%7D,'cvml','eorli...@gmail.com');>> wrote: >> >>> Hello, >>> >>> Gaston.jl is a plotting package based on gnuplot. Gnuplot is >>> command-line tool, so I send commands to it via a pipe. I open the pipe (on >>> Linux) with a ccall to "popen", and write gnuplot commands to the pipe >>> using a ccall to fputs. >>> >>> This works fine, but I'm trying to see if Julia's native pipe and stream >>> functionality can make this process more Julian and, in the process, more >>> cross-platform. The documentation is encouraging: >>> >>> "You can use [a Cmd] object to connect the command to others via pipes, >>> run it, and read or write to it." and "Julia provides a rich interface to >>> deal with streaming I/O objects such as terminals, pipes and TCP sockets." >>> Unfortunately, I just can't figure out how to use Julia's functionality for >>> this purpose. This is what I've tried (I am on Julia 0.3.9): >>> >>> First, I tried using `open` with read and write: >>> >>> julia> f=open(`gnuplot`,"r+") >>> ERROR: ArgumentError("mode must be \"r\" or \"w\", not \"r+\"") >>> >>> So I tried with write only: >>> >>> julia> f=open(`gnuplot`,"w") >>> (Pipe(open, 0 bytes waiting),Process(`gnuplot`, ProcessRunning)) >>> >>> So far, this looks good. I can see a gnuplot process running. >>> >>> Then I try to `write` to the pipe: >>> >>> julia> write(f,"plot sin(x)") >>> ERROR: `write` has no method matching write(::(Pipe,Process), >>> ::ASCIIString) >>> >>> OK, so let's try with `println`: >>> >>> julia> println(f,"plot sin(x)") >>> (Pipe(open, 0 bytes waiting),Process(`gnuplot`, ProcessRunning))plot >>> sin(x) >>> >>> and no plot is produced. >>> >>> I can't figure out how to read from the pipe, either: >>> >>> julia> readbytes(f) >>> ERROR: `readbytes` has no method matching readbytes(::(Pipe,Process)) >>> >>> julia> readall(f) >>> ERROR: `readall` has no method matching readall(::(Pipe,Process)) >>> >>> I'd appreciate any pointers. Thanks! >>> >>> -- mb >>> >>> >> >
