From: Kristof Bastiaensen <kristof@...>
Date: 2004-04-28T08:34:04+09:00
Subject: Re: popen issues


On Tue, 27 Apr 2004 17:16:24 -0600, Ara.T.Howard wrote:
>> Hi,
>> 
>> It is maybe not a good idea to use /bin/bash as a pipe, because it is an
>> interactive interpreter, and not made for pipe-communication.  Normally you
>> would just check for an end of file byte, but bash will not send you one.
>> Is there any reason to use bash?
> 
> really?  mine does:
> 
>   ~ > ruby -e 'p IO.popen("bash -c exit").eof?'
>   true
> 
> 
> how about you?
> 

Indeed, if you call bash with an argument it does.
But if you call just bash, like in the previous example, it
doesn't.  Instead of IO.popen("/bin/bash -c command"),
you could better do just IO.popen("command"), (unless of
course you want bash specific features).

Kristof

> -a
> 
>> 
>> 
>> On Wed, 28 Apr 2004 06:06:30 +0900, 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
>> 
>>