There is a number of command line arguments parsers in Ruby:
Personally I'd choose slop or optimist, those are not part of standard Ruby installation.
gem install slop
But it offers simplicity and code readability. Assuming slightly more complex example with required arguments and default values:
require 'slop'
begin
opts = Slop.parse do |o|
o.int '-a', '--age', 'Current age', default: 42
o.string '-f', '--first_name', 'The first name', required: true
o.string '-l', '--last_name', 'The last name', required: true
o.bool '-v', '--verbose', 'verbose output', default: false
o.on '-h','--help', 'print the help' do
puts o
exit
end
end
p opts.to_hash
rescue Slop::Error => e
puts e.message
end
optimist formerly known as trollop, it's very easy to ready, with minimum boilerplate code:
gem install optimist
require 'optimist'
opts = Optimist::options do
opt :verbose, "verbose mode"
opt :first_name, "The first name", type: :string, required: true
opt :last_name, "The last name", type: :string, required: true
opt :age, "Current age", default: 42
end
p opts
Similar example using OptionParser:
#!/usr/bin/env ruby
require 'optparse'
require 'ostruct'
begin
options = OpenStruct.new
OptionParser.new do |opt|
opt.on('-a', '--age AGE', 'Current age') { |o| options.age = o }
opt.on('-f', '--first_name FIRSTNAME', 'The first name') { |o| options.first_name = o }
opt.on('-l', '--last_name LASTNAME', 'The last name') { |o| options.last_name = o }
opt.on('-v', '--verbose', 'Verbose output') { |o| options.verbose = true }
end.parse!
options[:age] = 42 if options[:age].nil?
raise OptionParser::MissingArgument.new('--first_name') if options[:first_name].nil?
raise OptionParser::MissingArgument.new('--last_name') if options[:last_name].nil?
options[:verbose] = false if options[:verbose].nil?
rescue OptionParser::ParseError => e
puts e.message
exit
end
GetoptLong parsing is even more complicated:
require 'getoptlong'
opts = GetoptLong.new(
[ '--help', '-h', GetoptLong::NO_ARGUMENT ],
[ '--first_name', '-f', GetoptLong::REQUIRED_ARGUMENT ],
[ '--last_name', '-l', GetoptLong::REQUIRED_ARGUMENT ],
[ '--age','-a', GetoptLong::OPTIONAL_ARGUMENT ],
[ '--verbose','-v', GetoptLong::OPTIONAL_ARGUMENT ]
)
begin
options = {}
options[:verbose] = false
options[:age] = 42
opts.each do |opt, arg|
case opt
when '--help'
puts <<-EOF
usage: ./getlongopts.rb [options]
-a, --age Current age
-f, --first_name The first name
-l, --last_name The last name
-v, --verbose verbose output
-h, --help print the help
EOF
when '--first_name'
options[:first_name] = arg
when '--last_name'
options[:last_name] = arg
when '--age'
options[:age] = arg.to_i
when '--verbose'
options[:verbose] = arg
else
puts "unknown option `#{opt}`"
exit 1
end
end
raise GetoptLong::MissingArgument.new('Missing argument --first_name') if options[:first_name].nil?
raise GetoptLong::MissingArgument.new('Missing argument --last_name') if options[:last_name].nil?
rescue GetoptLong::Error => e
puts e.message
exit
end
puts options
Command line arguments was never meant to be a rocket science task, spend your time on reading/writing more useful code :)
