From: "Ara.T.Howard" <ahoward@...>
Date: 2004-04-28T06:54:04+09:00
Subject: Re: popen issues

On Wed, 28 Apr 2004, Hal Fulton wrote:

> Here's something I've never figured out.
> 
> Suppose I want real two-way communication with a process via popen.
> This seems doable.
> 
> But apparently the read hangs until I do a close_write; and if I
> do that, I can't write again. A flush doesn't work.
> 
> Here's what I was thinking (simplified):
> 
>    io = IO.popen("/bin/bash","r+") do |f|
>      f.puts "ls"
>      puts f.readlines
>      f.puts "date"
>      puts f.readlines
>    end
> 
> I even tried this (following) abomination, to no avail:
> 
>    io = IO.popen("/bin/bash","r+") do |f|
>      writer = f.dup
>      f.puts "ls\n"
>      f.close_write
>      puts f.readlines
>      w = writer.dup
>      w.puts "date\n"
>      w.close_write
>      puts f.readlines
>    end
> 
> 
> Can someone advise?
> 
> 
> Hal


~/tmp > ls
b.rb


~/tmp > cat b.rb
require 'session'
bash = Session::Bash.new

puts '---'
cmd = 'ls'
p cmd
o,e = bash.execute cmd 
p o
p e


puts '---'
cmd = 'date'
p cmd
bash.execute(cmd) do |o,e|
  o and p o
  e and p e
end

puts '---'
cmd = 'find'
bash.errproc = lambda{|e| p e}
bash.outproc = lambda{|o| p o}
bash.execute cmd


~/tmp > ruby b.rb
---
"ls"
"b.rb\n"
""
---
"date"
"Tue Apr 27 15:40:21 MDT 2004\n"
---
".\n"
"./b.rb\n"



it's horribly more complex than it first appears.  read the source to see why (RAA)

  - you don't know whey the output of one command starts and the next begins
  - you can't to non-blocking reads from threads
  - you can't send commands w/o blocking entire processs unless carefull

i believe my package is thread safe - as in it doesn't block them, not as in
many can use a session at once.  at least i using it for many multi-threaded
apps.

this took my over a week to write - you may want to save the trouble - the
source is really straight forward to read. (IMHO)

-a
-- 
===============================================================================
| EMAIL   :: Ara [dot] T [dot] Howard [at] noaa [dot] gov
| PHONE   :: 303.497.6469
| ADDRESS :: E/GC2 325 Broadway, Boulder, CO 80305-3328
| URL     :: http://www.ngdc.noaa.gov/stp/
| TRY     :: for l in ruby perl;do $l -e "print \"\x3a\x2d\x29\x0a\"";done 
===============================================================================