ruby命令行解析

可用库：getoptlong.rs， optionparser

对应类：GetoptLong, OptionParser

前者已过时，建议使用后者，且后者比前者易用。

后者特点：

1. 参数描述和代码处理写在一起

2. 输出参数说明，不需单独维护

3. 可选参数和命令参数描述简洁

4. 参数可自动转换为特定的类

5. 参数可限制在某个集合中

**************************************************************************

**************API（1.8.6）中的例子: example.rb**********************

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

class OptparseExample

    CODES = %w[iso-2022-jp shift_jis euc-jp utf8 binary]
    CODE_ALIASES = { "jis" => "iso-2022-jp", "sjis" => "shift_jis" }

    #
    # Return a structure describing the options.
    #
    def self.parse(args)
      # The options specified on the command line will be collected in *options*.     命令行的选项在options结构体中
      # We set default values here.
      options = OpenStruct.new
      options.library = []
      options.inplace = false
      options.encoding = "utf8"
      options.transfer_type = :auto
      options.verbose = false

      opts = OptionParser.new do |opts|
        opts.banner = "Usage: example.rb [options]"

        opts.separator ""
        opts.separator "Specific options:"

        # Mandatory argument.
        opts.on("-r", "--require LIBRARY",
                "Require the LIBRARY before executing your script") do |lib|
          options.library << lib
        end

        # Optional argument; multi-line description.
        opts.on("-i", "--inplace [EXTENSION]",
                "Edit ARGV files in place",
                " (make backup if EXTENSION supplied)") do |ext|
          options.inplace = true
          options.extension = ext || ''
          options.extension.sub!(//A/.?(?=.)/, ".") # Ensure extension begins with dot.
        end

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

        # Cast 'time' argument to a Time object.
        opts.on("-t", "--time [TIME]", Time, "Begin execution at given time") do |time|
          options.time = time
        end

        # Cast to octal integer.
        opts.on("-F", "--irs [OCTAL]", OptionParser::OctalInteger,
                "Specify record separator (default //0)") do |rs|
          options.record_separator = rs
        end

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

        # Keyword completion. We are specifying a specific set of arguments (CODES
        # and CODE_ALIASES - notice the latter is a Hash), and the user may provide
        # the shortest unambiguous text.
        code_list = (CODE_ALIASES.keys + CODES).join(',')
        opts.on("--code CODE", CODES, CODE_ALIASES, "Select encoding",
                " (#{code_list})") do |encoding|
          options.encoding = encoding
        end

        # Optional argument with keyword completion.
        opts.on("--type [TYPE]", [:text, :binary, :auto],
                "Select transfer type (text, binary, auto)") do |t|
          options.transfer_type = t
        end

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

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

        # No argument, shows at tail. This will print an options summary.
        # Try it and see!
        opts.on_tail("-h", "--help", "Show this message") do
          puts opts
          exit
        end

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

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

end # class OptparseExample

options = OptparseExample.parse(ARGV)
pp options

*************************************************************************************

*********************运行 ruby example.rb -h结果*******************************

Usage: example.rb [options]

Specific options:
    -r, --require LIBRARY            Require the LIBRARY before executing your s
cript
    -i, --inplace [EXTENSION]        Edit ARGV files in place
                                       (make backup if EXTENSION supplied)
        --delay N                    Delay N seconds before executing
    -t, --time [TIME]                Begin execution at given time
    -F, --irs [OCTAL]                Specify record separator (default /0)
        --list x,y,z                 Example 'list' of arguments
        --code CODE                  Select encoding
                                       (sjis,jis,iso-2022-jp,shift_jis,euc-jp,ut
f8,binary)
        --type [TYPE]                Select transfer type (text, binary, auto)
    -v, --[no-]verbose               Run verbosely

Common options:
    -h, --help                       Show this message
        --version                    Show version

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