Popen, open3 problems

ruby-talk
1

Hi,

I think this problem is surely solved but hven't found anything on the net:

I get two programs:
1. a ruby (master)
2. a perl (slave)

I want the master to set commands to the slave and wait for the answer
(repeatedly). So a conversation could look like this:

m: set_var
m: v=8
s: set
m: get_var
m: v
s: 8
...

The problem is that ruby refuses to write to stdin of the slave until I
close the pipe. But I want to use the pipe repeatedly. Did I miss
something about IPC?

Thanks

My curent progs look like this:

require 'fcntl'
require 'open3'

pin, pout, perr = Open3.popen3('perl test.pl')
    pin.fcntl(Fcntl::F_SETFL, Fcntl::O_NONBLOCK)
    pout.fcntl(Fcntl::F_SETFL, Fcntl::O_NONBLOCK)
    perr.fcntl(Fcntl::F_SETFL, Fcntl::O_NONBLOCK)

pin.syswrite "set_var\n"
pin.syswrite "v=8\n"
#pin.close_write #<----------don't want to do this but have to!
result=pout.readline
puts result
#pin.close
pout.close
perr.close

···

---------------------------------------------------------------------------
perl slave:

while ($line = <STDIN>) { #first line is the command
chomp($line);
if ($line eq "set_var") { &set_var;}
elsif ($line eq "quit") { exit 0;}
}

sub set_var {
$var=<STDIN>; #second...lines are the params; get the var
chomp($var);
print "set."; #return a confirmation
}

2

Hi,

I think this problem is surely solved but hven't found anything on the net:

I get two programs:
1. a ruby (master)
2. a perl (slave)

I want the master to set commands to the slave and wait for the answer
(repeatedly). So a conversation could look like this:

m: set_var
m: v=8
s: set
m: get_var
m: v
s: 8
...

The problem is that ruby refuses to write to stdin of the slave until I
close the pipe. But I want to use the pipe repeatedly. Did I miss
something about IPC?

   man stdio
   /buffer

My curent progs look like this:

require 'fcntl'
require 'open3'

     harp:~ > cat a.rb
     require 'open3'

     Open3.popen3 "perl a.pl" do |i,o,e|
       i.puts 'set_var'
       i.puts 'v=8'
       i.flush # <<---

       puts o.gets
     end

     harp:~ > cat a.pl

     $| = 1; # <<---

     while ($line = <STDIN>) {
       chomp($line);
       if ($line eq "set_var") { &set_var;}
       elsif ($line eq "quit") { exit 0;}
     }

     sub set_var { $var=<STDIN>; chomp($var); print "set.$var\n"; }

     harp:~ > ruby a.rb
     set.v=8

-a

···

On Fri, 17 Nov 2006, Peter Schrammel wrote:
--
my religion is very simple. my religion is kindness. -- the dalai lama

3

Peter Schrammel wrote:

/ ...

pin.syswrite "set_var\n"
pin.syswrite "v=8\n"
#pin.close_write #<----------don't want to do this but have to!

Have you tried "pin.flush" ?

···

--
Paul Lutus
http://www.arachnoid.com

4

Are you sure it's that Ruby didn't send the data, and not that perl
didn't answer yet?

I.e., have you tried setting $| on the perl side?
http://perl.plover.com/FAQs/Buffering.html

I love perl, it's an awesome language, but unfortunately there are many
magic nooks and crannies.

lg, Bernd

···

Peter Schrammel <peter.schrammel@gmx.de> wrote:

The problem is that ruby refuses to write to stdin of the slave until I
close the pipe. But I want to use the pipe repeatedly. Did I miss
something about IPC?

5

...

      i.puts 'v=8'
      i.flush # <<---

ok. i don't need this if I use syswrite (flush flushes only ruby buffers)

      puts o.gets
    end

    harp:~ > cat a.pl

    $| = 1; # <<---

yes! that's it. I knew there was some perl-guru-thing about it.

    while ($line = <STDIN>) {
      chomp($line);
      if ($line eq "set_var") { &set_var;}
      elsif ($line eq "quit") { exit 0;}
    }

    sub set_var { $var=<STDIN>; chomp($var); print "set.$var\n"; }

    harp:~ > ruby a.rb
    set.v=8

thanks very much.

···

ara.t.howard@noaa.gov wrote: