From: Robert Klemme <shortcutter@...>
Date: 2010-01-07T22:20:05+09:00
Subject: Re: which shell?

On 01/07/2010 01:33 PM, Wybo Dekker wrote:
> It looks like Kernel#system uses sh, not bash, even though I told linux to use bash:
> 
> #!/usr/bin/env ruby
> system("echo $SHELL")
> system("ls -d /{etc,sbin}")
> 
> =>
> 
> /bin/bash
> ls: cannot access /{etc,sbin}: No such file or directory
> 
> How can I tel system to use bash?

If I would want to enforce a particular shell I would always explicit 
invoke it and not rely on the environment shell set appropriately (your 
script will otherwise break immediately if someone uses a different 
shell).  Here's one way to do it:

robert@fussel:~$ ruby19 -e "system('bash','-c','ls -d /{etc,sbin}')"
/etc  /sbin

But you don't really need a shell for this.  In your case you could as 
well do this:

robert@fussel:~$ ruby19 -e 'p Dir["/{etc,sbin}"]'
["/etc", "/sbin"]

or even

robert@fussel:~$ ruby19 -e 'p %w{/etc /sbin}.select{|d| test ?d, d}'
["/etc", "/sbin"]

or more verbose

robert@fussel:~$ ruby19 -e 'p %w{/etc /sbin}.select{|d| File.directory? d}'
["/etc", "/sbin"]

...

I can't really think of a reason to fork a particular shell from a Ruby 
script other than for executing an existing shell script (in which case 
it is taken care of automatically provided you have the proper shebang 
line).  All other tasks are probably done more efficiently from inside 
the interpreter.

Kind regards

	robert


-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/