如何指定所需的开关（未参数）使用Ruby OptionParser？ [英] How do you specify a required switch (not argument) with Ruby OptionParser?

问题描述

我在写一个脚本，我想需要一个 - 价值与主机开关，但如果 - 主机开关没有指定我想解析失败的选项。

I'm writing a script and I want to require a --host switch with value, but if the --host switch isn't specified I want the option parsing to fail.

我似乎无法弄清楚如何做到这一点。该文档似乎只指定如何使参数值强制性的，不是交换机本身。

I can't seem to figure out how to do that. The docs seem to only specify how to make the argument value mandatory, not the switch itself.

推荐答案

我假设你正在使用optparse这里，虽然同样的技术将用于其他选项解析库工作。

I am assuming you are using optparse here, although the same technique will work for other option parsing libraries.

最简单的方法可能是使用所选的选项解析库来解析参数，然后引发OptionParser :: MissingArgument异常，如果主机的价值为零。

The simplest method is probably to parse the parameters using your chosen option parsing library and then raise an OptionParser::MissingArgument Exception if the value of host is nil.

以下code说明

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

options = {}

optparse = OptionParser.new do |opts|
  opts.on('-h', '--host HOSTNAME', "Mandatory Host Name") do |f|
    options[:host] = f
  end
end

optparse.parse!

#Now raise an exception if we have not found a host option
raise OptionParser::MissingArgument if options[:host].nil?


puts "Host = #{options[:host]}"

与运行一个命令行这个例子

Running this example with a command line of

./program -h somehost

简单显示主机=，某

simple displays "Host = somehost"

尽管用缺失-h运行，没有文件名产生以下输出

Whilst running with a missing -h and no file name produces the following output

./program:15: missing argument:  (OptionParser::MissingArgument)

和与./program -h命令行运行产生

And running with a command line of ./program -h produces

/usr/lib/ruby/1.8/optparse.rb:451:in `parse': missing argument: -h (OptionParser::MissingArgument)
  from /usr/lib/ruby/1.8/optparse.rb:1288:in `parse_in_order'
  from /usr/lib/ruby/1.8/optparse.rb:1247:in `catch'
  from /usr/lib/ruby/1.8/optparse.rb:1247:in `parse_in_order'
  from /usr/lib/ruby/1.8/optparse.rb:1241:in `order!'
  from /usr/lib/ruby/1.8/optparse.rb:1332:in `permute!'
  from /usr/lib/ruby/1.8/optparse.rb:1353:in `parse!'
  from ./program:13

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