open source and deployment

I apologize in advance for those of you who don't particularly care to read any code.

But one of the things I'm going to try to do while working on my startup is to post as many code snippets as possible.

Why? Because I'm a believer in open source. My startup is not focussed around building great deployment tools. By posting my code, I'm helping other people who also need to solve similar issues. At the same time, there's a good chance that someone smarter than me will read this and tell me a much simpler or more elegant way of achieving the same result.

If it starts taking up too much of my time, I might post less stuff. If I start to see value in posting code, I might try to do more of it. Either way, I'm running as fast as I can to build an amazing product.

The following script should help me to write common config files and test them out on my mac first and then deploy them with no changes. See the usage function for more info.

Oh - and I'm still a newbie ruby programmer. So if you have code suggestions, or if there's a tool that already does what this does, then let me know. I have no qualms about throwing away my code and using someone else's. Less code = less bugs.

#!/usr/bin/env ruby
require 'yaml'

def usage( msg )
  STDERR.puts msg
  STDERR.puts <<EOF

USAGE
        generate <config_file> <stage> files..

DESCRIPTION
        Given the following config.yml:
--
test:
 base: path1
 user: name1
prod:
 base: path2
 user: name2
--
        and a lighttpd.conf:

--
server.username            = "$user$"
server.document-root       = "$base$/public_html"
--

% generate config.yml test lighttpd.conf 
 will create the file lighttpd.conf.generated which looks like:

--
server.username            = "name1"
server.document-root       = "path1/public_html"
--

EOF
  exit
end

usage() if( ARGV.size < 3 )

config_file = ARGV.shift
stage = ARGV.shift

usage( "config file #{config_file} not found. " ) unless File.exists?( config_file ) 

all_config = YAML.load_file( config_file )

unless( all_config.has_key?( stage ) ) 
  usage("config file #{config_file} doesn't specify stage '#{stage}'.") 
end

config = all_config[stage]

# build up the regexp to match all identifiers:
regexp_string = '('
config.each_key { |id|
  regexp_string += '\$' + id + '\$|'
}
regexp_string.chop! 
regexp_string += ')'
matcher = Regexp.new( regexp_string )


# Iterate through each file
ARGV.each { |filename|
  unless( File.exists?( filename ) ) 
    STDERR.puts "file '#{filename}' not found. continuing"
    next
  end
  g_filename = filename + '.generated'
  if( File.exists?( g_filename ) )
    # TODO: move old file out of the way instead..
    STDERR.puts "file '#{g_filename}' exists. OVERWRITING!"
  end

  generated = File.new( g_filename, "w" )
  # check each line
  File.open(filename).each_line{ |line|
    # replace each instance of a token
    line.gsub!( matcher ) { |match|
      id = match[1..(match.size - 2)]
      # with the value specified in the config file
      config[id]
    }
    generated.puts( line )
  }
}