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
