Tag Archive for ‘rubygems’ at Ruby Blender

At various points in my life, I’ve used many methods of parsing command line options, from rolling my own, to using getopt or other libraries. Recently I came across a new one which has its own view of how to parse commandline arguments.

Trollop is, as they put it, “Yet Another Fine CommandLine Argument Parsing Library” (YAFCLAP). It’s goal is to be as easy as possible. You can install it as a single file in lib, or use it as a gem. Trollop doesn’t care. To install, you can download it from rubyforge, or use the ever popular:

gem install trollop

(you may need to prepend sudo, or run it as root).

Let’s take a look at a simple example:

require 'rubygems' require 'trollop' opts = Trollop::options do opt :host, "Host to connect to", :default => "localhost" opt :port, "jmx remote port", :default => 4444 opt :interval, "How often do we poll (in seconds)", :default => 10 opt :count, "How many intervals, 0 == infinite, use ^C (SIGINT) to exit and write output", :default => 0 end p opts

The first argument to opt is the name of the option. We don’t have to specify a switch; it’s smart enough to figure out a mapping for them. The second is a description of the argument. You can specify a default value and/or a type. In this example, we’ve specified defaults. And here it is in use:

$ ruby trollop_simple.rb {:interval=>10, :count=>0, :help=>false, :host=>"localhost", :port=>4444} $ ruby trollop_simple.rb -h Error: option '-h' needs a parameter. Try --help for help. $ ruby trollop_simple.rb --help Options: --host, -h : Host to connect to (default: localhost) --port, -p : jmx remote port (default: 4444) --interval, -i : How often do we poll (in seconds) (default: 10) --count, -c : How many intervals, 0 == infinite, use ^C (SIGINT) to exit and write output (default: 0) --help, -e: Show this message

Notice that it has set up mappings for us as well as created a nicely formatted help — though it’s a default, without a lot of information. Let’s add a version and usage:

require 'rubygems' require 'trollop' opts = Trollop::options do version < "localhost" opt :port, "jmx remote port", :default => 4444 opt :interval, "How often do we poll (in seconds)", :default => 10 opt :count, "How many intervals, 0 == infinite, use ^C (SIGINT) to exit and write output", :default => 0 end p opts

Now let’s see what we have:

$ ruby trollop_simple.rb --help jmx_mon is a program to monitor a jmx bean's value over time. It can output the data as a csv, a graph in a pdf, or both.
Usage jmx_mon [options] where [options] are: --host, -h : Host to connect to (default: localhost) --port, -p : jmx remote port (default: 4444) --interval, -i : How often do we poll (in seconds) (default: 10) --count, -c : How many intervals, 0 == infinite, use ^C (SIGINT) to exit and write output (default: 0) --version, -v: Print version and exit --help, -e: Show this message $ ruby trollop_simple.rb -v jmx_mon -- we be jammin' with version zz9-za aka Arthur Dent Don't forget your towel!

We now have a nicer usage, as well as version. Also, it will stop automagickally if we ask for help or the version.

All of the options are placed in the opts hash; let’s see what we can do with it:

require 'rubygems' require 'trollop'
aliases = { :MEMORY_HEAP => "Heap memory usage, multiple values", :MEMORY_HEAP_USED => "Used heap memory" } opts = Trollop::options do version < "localhost" opt :port, "jmx remote port", :default => 4444 opt :interval, "How often do we poll (in seconds)", :default => 10 opt :count, "How many intervals, 0 == infinite, use ^C (SIGINT) to exit and write output", :default => 0 opt :aliases, "Print defined bean aliases & exit.", :default => false opt :towel, "Don't forget this!", :default => false end if opts[:aliases_given] aliases.each_pair do |key, value| puts "#{key}: #{value}" end exit end Trollop::die :towel, "You forgot your towel. You've been eaten by a Ravenous Bugblatter Beast of Traal" unless opts[:towel]
p opts

We’ve added two more options, one for printing out aliases, and another indicating whether or not you have your towel — with deadly results should you forget.

$ ruby trollop_simple.rb -a MEMORY_HEAP: Heap memory usage, multiple values MEMORY_HEAP_USED: Used heap memory
$ ruby trollop_simple.rb Error: argument --towel You forgot your towel. You've been eaten by a Ravenous Bugblatter Beast of Traal. Try --help for help.

There’s more that you can do with trollop; the website and documentation gives more examples. However, I’d suggest considering trollop the next time you need to parse the command line.

Here’s my (current) .irbrc, with comments

# I am including gems in my irb session. Therefore, the next require require 'rubygems'


# wirble is a wonderful gem which add nice features to irb

require 'wirble'
# Dr. Nic's useful helper gem.  It makes it so you can say:

#   foo.map_by_bar

# instead of having to say:

#   foo.map{|f| f.bar}

# more to the point you can do

#   people.map_by_first_and_last

# instead of

#   people.map{|p| [p.first, p.last]}

require 'map_by_method'
# what_methods is a way to see which methods, when performed on an object, return a particular value:

# >> "hi".what? 'h'

# "hi".chop! == "h"

# "hi".chop == "h"

# => ["chop!", "chop"]

require 'what_methods'
# pretty print --> provides a "pretty" view of an object

require 'pp'
# auto indent irb; it's useful for when you're just experimenting

IRB.conf[:AUTO_INDENT]=true
# start wirble (with color)

Wirble.init

#Wirble.colorize
# What are the methods which belong only to an object, and not those inherited from Object

class Object

  def my_methods

    (self.methods - Object.methods).sort

  end

end

# strip html tags from a string class String def strip_tags self.gsub(/<\S[^><]*>/,"") end end

I’ve shown mine. Show me yours?

Here are links to the referenced rubygems:

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Tag Archive for 'rubygems'

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