From: Guillaume Marcais <guslist@...>
Date: 2005-05-13T07:40:02+09:00
Subject: Re: Nuby: 'importing shell script variables' eval/proc/binding

On Fri, 2005-05-13 at 06:00 +0900, Dany Cayouette wrote:
> Greetings,
>    I'm pretty sure eval/proc/binding needs/can be used to solve my 
> problem, but I'm having difficulty grasping those concepts.
> 
> Given a series of shell scripts (bourne based) containing code such as
> 
> FIRST=Dany
> LAST='Cayouette'
> FULLNAME="$FIRST $LAST"
> UID="danyc ($FULLNAME)"
> 
> I would like to 'import' those value into a Ruby Hash such that the end 
> result is something like
> {"LAST"=>"Cayouette", "UID"=>"danyc (Dany Cayouette)", "FULLNAME"=>"Dany 
> Cayouette", "FIRST"=>"Dany"}
> 
> So far I have
> class Hash
>    def shparse (file)
>      File.open(file, "r") do  |f|
>        while line = f.gets
>          next unless line =~ /^\s*(\w+)=(.*)$/
>          k = $1
>          v = $2
>          self[k] = v
>        end
>      end
>     p self
>     self
>    end
> end

Two solutions to you problem. The first one shell_expand actually calls
the shell. So the expansion should be exactly what it is supposed to be.
But it is probably fragile: on my system, the variable UID is already
defined and read-only, and it would break shell_expand. 

The other one tries to mimic the shell variable expansion in ruby. Of
course, not all the shell expansions are performed (as seen with
SHELL_ONLY).

$ cat shell-expand.rb
#!/usr/bin/ruby -w

script = <<EOT
FIRST=Dany
LAST='Cayouette'
FULLNAME="$FIRST $LAST"
UUID="danyc ($FULLNAME)"
EMPTY=

 junk foo
SHELL_ONLY=$(date)
EOT

def shell_expand(script)
  res = { }
  io = open("|/bin/sh", "r+")
  script.each { |l|
    next unless l =~ /^(\w+)\s*=/
    io.puts(l.chomp)
    io.puts("echo $#{$1}")
    res[$1] = (io.gets || "").chomp
  }
  res
end

def self_expand(script)
  res = { }
  script.each { |l|
    next unless l =~ /^(\w+)\s*=\s*['"]?(.*?)['"]?$/
    k, v = $1.strip, $2.strip
    v = v.gsub(/\$(\w+)/) { |m| res[$1] || "" }
    res[k.strip] = v
  }
  res
end

p shell_expand(script)
p self_expand(script)


$ ruby shell-expand.rb
{"EMPTY"=>"", "LAST"=>"Cayouette", "FULLNAME"=>"Dany Cayouette",
"SHELL_ONLY"=>"Thu May 12 18:33:56 EDT 2005", "UUID"=>"danyc (Dany
Cayouette)", "FIRST"=>"Dany"}
{"EMPTY"=>"", "LAST"=>"Cayouette", "FULLNAME"=>"Dany Cayouette",
"SHELL_ONLY"=>"$(date)", "UUID"=>"danyc (Dany Cayouette)",
"FIRST"=>"Dany"}

Hope it helps,
Guillaume.