a mirrored timocracy

Feb 25

Using open3 in ruby to call an interactive shell command with all three pipes while avoiding block

Apparently when using the three standard pipes (stdin, stdout, stderr)
in your own programming, it is REALLY easy to block or deadlock on
them. At first I figured there were problems in the ruby *open3 
library, but this is not ruby specific, I found message board
discussions about similar problems using perl open3 libraries.

Trying to figure out these quirks is made harder by the fact that all
of the common ruby examples are non-interactive, and just close the
stdin before trying to read any output. Even worse, many, many shell
programs don’t use stderr and stdout in what I understood as the
proper way. For instance I first as trying to use ftp as the command,
but this proved beyond my abilities. I then came up with a simple
working example that calls dc (the simple reverse polish calculator
available on most unixes), and discovered that on errors it outputs to
both stderr and stdout (different text). I was not able to in any way
to get the output from stderr until I closed stdin (short of
redirecting stderr to a temp file).

This drives home the point that you shouldn’t be doing this too much,
in ruby. Generally, use a better, task-specific ruby library, for
these sort of tasks. If you want to use ftp, use net-ftp, for
instance. If you want to use more extensive interactive shell
sessions, check out Ara Howard’s session
gem 
 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 
#http://github.com/ahoward/open4 is an alternative that handles pid and exit status
#http://github.com/ahoward/session a more fleshed our shell utility
require ‘open3’
 
Open3.popen3(“dc”) do |stdin, stdout, stderr|
  t = Thread.new(stderr) do |terr|
    while (line = terr.gets)
      puts “stderr: #{line}”
    end
  end
  
  puts “pushing 5 to stack”
  stdin.puts(5)
  puts “pushing 10 to stack”
  stdin.puts(10)
  puts “pushing + to stack”
  stdin.puts(”+”)
  puts “sending print command”
  stdin.puts(“p”)
  result = stdout.gets
  puts “stdout: #{ result }”
  
  puts “\ntrying an unsupported command”
  stdin.puts(“b”)
 
 
  extra_info_not_in_stderror = stdout.gets
  puts “stdout: #{extra_info_not_in_stderror}”
 
 
  puts “\nclosing stdin to avoid deadlock with stderr”
  stdin.close
 
  # puts “let’s give stderr a chance to run”
  # t.run or sleep 1
  
  puts “joining”
  t.join
end
  		 
 *Open3 as a naming convention tends to be a library to call shell 
commands with the three aforementioned pipes.      
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                    Feb 15
                

            
        
            

                
                    
Call a custom jar from ruby in jruby

                    
  
  
 1 2 3 4 5 6 7 8 9 
 		   
#javac HelloWorld.java && jar cvf HelloWorld.jar HelloWorld.class
require ‘java’ 
require ‘HelloWorld.jar’ 
import ‘HelloWorld’
 
puts HelloWorld.new.hello 
#=> “Hello cruel world”
 
#jruby hello_world.rb
  		 
      
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Call a custom jar from ruby in jruby #ruby #tech #jruby

                    
  
  
 1 2 3 4 5 6 7 8 9 
 		   
#javac HelloWorld.java && jar cvf HelloWorld.jar HelloWorld.class
require ‘java’ 
require ‘HelloWorld.jar’ 
import ‘HelloWorld’
 
puts HelloWorld.new.hello 
#=> “Hello cruel world”
 
#jruby hello_world.rb
  		 
      
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                    Feb 13
                

            
        
            

                
                    
Making config.gem in Rails 2.3.x allow you to install from a direct url or the local filesystem

                    
If you are on Rails 2.3.x (pre-Bundler) and want to organize some of your shared functionality into gems, but they are for internal use only, you could set-up a private gem server and point the :source at this server.  And then you could deal with authentication, and then…
  
Or as a quick hack you could just allow for config.gem to reference the gemfile directly, which would then mean ‘rake gems:install’ would work, even if the gem were stored locally, or on a file-server, etc.  Also useful as you could then just point at a .gem file on github.
  
  
  
 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 
 		   
## require in config/environment.rb before init starts
#require ‘config/add_explicit_path_to_config_gem’
#Rails::Initializer.run do |config|
#config.gem ‘my_gem’, :version => ‘0.0.1’, :explicit_path => “#{RAILS_ROOT}/vendor/local_gemfiles/my_gem-0.0.1.gem” #or
#config.gem ‘my_gem’, :version => ‘0.0.1’, :explicit_path => “http://github.com/myname/myrepo/raw/master/mygem.gem” #or
 
module Rails
  class GemDependency
    def initialize_with_explicit_path(name, options = {})
      @explicit_path = options[:explicit_path]
      initialize_without_explicit_path(name, options = {})
    end
    alias_method_chain :initialize, :explicit_path
    
  private
  
    def install_command
      cmd = %w(install) « (@explicit_path || name)
      cmd « “—version” « %(“#{requirement.to_s}”) if requirement
      cmd « “—source”  « @source  if @source
      cmd
    end
  end
end
  		 
      
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                    Feb 10
                

            
        
            

                
                    
“Object is not missing constant XXX” and “A copy of YYY has been removed from the module tree but is still active” when using Rails metal

                    
If you have a Rails metals that has enough code to have its own subdirectories that live in your Rails load_paths you can get stuck in dependency hell. The combinations of autoloading, rails reloading on development, and running through the metal can intersect in nasty ways: on the first request you get “Object is not missing constant XXX” and subsequent requests kick off “A copy of YYY has been removed from the module tree but is still active.”
  
The easiest solution is to kill magic reloading for this metal’s code by adding the metal’s directories of code to the Rails load_once_paths and then using explicit require_dependency calls for any files that give you trouble. For example, I have a MadMetal that referenced a Mad which has a whole sub-directory structure of code that, for now, lives under lib/mad:
  
#config/environment.rb  config.load_once_paths += Dir["#{RAILS_ROOT}/lib/mad/**/"]    #app/metal/mad_metal.rb  require_dependency 'mad'  class MadMetal  def self.call(env)  if (env["PATH_INFO"] == '/the_path_to_my_metal')  Mad.call(env)  else  [404, {"Content-Type" => "text/html"}, ["Not Found"]]  end  end  end
  
And wallah, no more conflicts between development auto-reloading and metal.
  
Of course, now you need to restart the server if you change code in lib/mad. In this case it’s not a problem for me because the app is also a stand-alone rack app that I run with shotgun when I want development environment reloading.
      
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“Object is not missing constant XXX” and “A copy of YYY has been 	removed from the module tree but is still active” when using Rails metal

                    
If you have a Rails metals that has enough code to have it’s own 
subdirectories that live in your Rails load_paths you can get stuck in 
dependency hell. The combinations of autoloading, rails reloading on 
development, and running through the metal can intersect in nasty 
ways: on the first request you get “Object is not missing constant 
XXX” and subsequent requests kick off “A copy of YYY has been removed 
from the module tree but is still active.”  The easiest solution is to kill magic reloading for this metal’s code; 
add the metal’s directories of code to the Rails load_once_paths and 
then use explicit require_dependency calls for any files that give you 
trouble. For example, I have a MadMetal that referenced a Mad which 
has a whole sub-directory structure of code that, for now, lives under 
lib/mad: 
 
#environment.rb 
config.load_paths += Dir["#{RAILS_ROOT}/lib/mad/**/"]" 
 #app/metal/mad_metal.rb 
require_dependency 'mad' 
class MadMetal 
 def self.call(env) 
 if (env["PATH_INFO"] == '/mad/') 
 Mad.call(env) 
 else 
 [404, {"Content-Type" => "text/html"}, ["Not Found"]] 
 end 
 end 
end 
  And wallah, no more conflicts between development auto-reloading and metal. 
 Of course, now you need to restart the server if you change code in 
lib/mad. In this case it’s not a problem for me because the app is 
also a stand-alone rack app that I run with shotgun when I want development environment reloading.      
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                    Feb 02
                

            
        
            

                
                    
Tagging a git release with current branch name and date

                    
Either add this to your .git/config
  
[alias]  datetag = !git tag `git name-rev --name-only HEAD`-`date \"+%Y%m%d%H%M\"`
  
or run it in your project folder to add it to the config for that project:
  
git config alias.datetag '!git tag `git name-rev --name-only HEAD`-`date "+%Y%m%d%H%M"`'
      
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Tagging a git release with current branch name and date

                    
Either add this to your .git/config [alias]:
  
datetag = !git tag `git name-rev --name-only HEAD`-`date \"+%Y%m%d%H%M\"`
  
or run it in your project folder to add it to the config for that project:
  
git config alias.datetag '!git tag `git name-rev --name-only HEAD`-`date "+%Y%m%d%H%M"`'
      
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Setting RAILS_ENV on Dreamhost when running Passenger

                    
It may depend on which server you are on, but mine has mod_env 
enabled, so it’s a simple matter of setting the ENV[‘RAILS_ROOT’] in 
an .htacess file 
 
SetEnv RAILS_ENV staging
      
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Setting RAILS_ENV on Dreamhost when running Passenger

                    
It may depend on which server you are on, but mine has mod_env 
enabled, so it’s a simple matter of setting the ENV[‘RAILS_ROOT’] in 
an .htacess file 
 
SetEnv RAILS_ENV staging
      
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