SystemExit 是一种特殊的异常吗？

发布于 2024-10-19 03:33:59 字数 296 浏览 3 评论 0原文

SystemExit 的行为与其他 Exception 有何不同？我想我理解为什么提出适当的异常不好的一些原因。例如，您不希望发生这样的奇怪事情：

begin
  exit
rescue => e
  # Silently swallow up the exception and don't exit
end

但是如何救援会忽略SystemExit？（它使用什么标准？）

原文

How does SystemExit behave differently from other Exceptions? I think I understand some of the reasoning about why it wouldn't be good to raise a proper Exception. For example, you wouldn't want something strange like this to happen:

begin
  exit
rescue => e
  # Silently swallow up the exception and don't exit
end

But how does the rescue ignore SystemExit? (What criteria does it use?)

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残花月 2024-10-26 03:33:59

当您编写没有一个或多个类的 rescue 时，它与编写相同：

begin
  ...
rescue StandardError => e
  ...
end

但是，有些异常不是从 StandardError 继承的。 SystemExit 是其中之一，因此不会捕获它。以下是 Ruby 1.9.2 中层次结构的子集，您可以自己查找< /a>：

BasicObject
  Exception
    NoMemoryError
    ScriptError
      LoadError
        Gem::LoadError
      NotImplementedError
      SyntaxError
    SecurityError
    SignalException
      Interrupt
    StandardError
      ArgumentError
      EncodingError
        Encoding::CompatibilityError
        Encoding::ConverterNotFoundError
        Encoding::InvalidByteSequenceError
        Encoding::UndefinedConversionError
      FiberError
      IOError
        EOFError
      IndexError
        KeyError
        StopIteration
      LocalJumpError
      NameError
        NoMethodError
      RangeError
        FloatDomainError
      RegexpError
      RuntimeError
      SystemCallError
      ThreadError
      TypeError
      ZeroDivisionError
    SystemExit
    SystemStackError
    fatal

因此，您可以使用以下方式捕获仅 SystemExit：

begin
  ...
rescue SystemExit => e
  ...
end

...或者您可以选择捕获每个异常，包括SystemExit with：

begin
  ...
rescue Exception => e
  ...
end

自己尝试一下：

begin
  exit 42
  puts "No no no!"
rescue Exception => e
  puts "Nice try, buddy."
end
puts "And on we run..."

#=> "Nice try, buddy."
#=> "And on we run..."

请注意，此示例在（某些版本的？）IRB 中不起作用，IRB 提供了自己的退出方法来屏蔽正常的 Object#exit。

在 1.8.7 中：

method :exit
#=> #<Method: Object(IRB::ExtendCommandBundle)#exit>

在 1.9.3 中：

method :exit
#=> #<Method: main.irb_exit>

When you write rescue without one or more classes, it is the same as writing:

begin
  ...
rescue StandardError => e
  ...
end

There are Exceptions that do not inherit from StandardError, however. SystemExit is one of these, and so it is not captured. Here is a subset of the hierarchy in Ruby 1.9.2, which you can find out yourself:

BasicObject
  Exception
    NoMemoryError
    ScriptError
      LoadError
        Gem::LoadError
      NotImplementedError
      SyntaxError
    SecurityError
    SignalException
      Interrupt
    StandardError
      ArgumentError
      EncodingError
        Encoding::CompatibilityError
        Encoding::ConverterNotFoundError
        Encoding::InvalidByteSequenceError
        Encoding::UndefinedConversionError
      FiberError
      IOError
        EOFError
      IndexError
        KeyError
        StopIteration
      LocalJumpError
      NameError
        NoMethodError
      RangeError
        FloatDomainError
      RegexpError
      RuntimeError
      SystemCallError
      ThreadError
      TypeError
      ZeroDivisionError
    SystemExit
    SystemStackError
    fatal

You can thus capture just SystemExit with:

begin
  ...
rescue SystemExit => e
  ...
end

...or you can choose to capture every exception, including SystemExit with:

begin
  ...
rescue Exception => e
  ...
end

Try it yourself:

begin
  exit 42
  puts "No no no!"
rescue Exception => e
  puts "Nice try, buddy."
end
puts "And on we run..."

#=> "Nice try, buddy."
#=> "And on we run..."

Note that this example will not work in (some versions of?) IRB, which supplies its own exit method that masks the normal Object#exit.

In 1.8.7:

method :exit
#=> #<Method: Object(IRB::ExtendCommandBundle)#exit>

In 1.9.3:

method :exit
#=> #<Method: main.irb_exit>

回复收藏 0 原文

孤独患者 2024-10-26 03:33:59

简单示例：

begin
  exit
  puts "never get here"
rescue SystemExit
  puts "rescued a SystemExit exception"
end

puts "after begin block"

退出 status / success? 等也可以读取：

begin
  exit 1
rescue SystemExit => e
  puts "Success? #{e.success?}" # Success? false
end

begin
  exit
rescue SystemExit => e
  puts "Success? #{e.success?}" # Success? true
end

方法的完整列表：[:status, :success?, :exception, ：消息，：backtrace，：backtrace_locations，：set_backtrace，：原因]

Simple example:

begin
  exit
  puts "never get here"
rescue SystemExit
  puts "rescued a SystemExit exception"
end

puts "after begin block"

The exit status / success?, etc. can be read too:

begin
  exit 1
rescue SystemExit => e
  puts "Success? #{e.success?}" # Success? false
end

begin
  exit
rescue SystemExit => e
  puts "Success? #{e.success?}" # Success? true
end

Full list of methods: [:status, :success?, :exception, :message, :backtrace, :backtrace_locations, :set_backtrace, :cause]

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