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Saturday, 4 July 2009

Ruby Parsing Command Line Options

Ruby has built in methods for dealing with parsing command line options, it is called optparse.

optparse rdocs

some optparse examples

A Small example (cut down from the above) showing most common requirments.
Also on github.

#!/usr/bin/env ruby

require 'optparse'
require 'optparse/time'
require 'ostruct'
require 'pp'

class OptparseExample

# Return a structure describing the options.
def self.parse(args)
# The options specified on the command line will be collected in *options*.
# We set default values here.
options =

options.verbose = false
options.time = 0
options.delay = 0
options.leftovers = nil

opts = do |opts|
opts.banner = "Usage: example.rb [options]"
opts.separator ""
opts.separator "Specific options:"

# Boolean switch.
opts.on("-v", "--[no-]verbose", "Run verbosely") do |v|
options.verbose = v

# Cast 'time' argument to an integer.
opts.on("-t", "--time [TIME]", Integer, "Begin execution at given time") do |time|
options.time = time

# Cast 'delay' argument to a Float.
opts.on("--delay N", Float, "Delay N seconds before executing") do |n|
options.delay = n

# List of arguments.
opts.on("--list x,y,z", Array, "Example 'list' of arguments") do |list|
options.list = list

opts.separator ""
opts.separator "Common options:"

# No argument, shows at tail. This will print an options summary.
opts.on_tail("-h", "--help", "Show this message") do
puts opts

# Another typical switch to print the version.
opts.on_tail("--version", "Show version") do
#puts OptionParser::Version.join('.')
puts "Version 0.1.0"

options.leftovers = opts.parse!(args)
end # parse()

end # class OptparseExample

options = OptparseExample.parse(ARGV)
pp options
puts ""
puts ""
puts options.leftovers

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