ruby - "$-w = true"是做什么的？

Question

我一直在阅读 Rack 的源代码，并且在 server.rb我发现:

$-w = true

它正在为全局变量赋值。文档说:

Options may include:
    # * :warn
    #     turn on warnings ($-w = true)

但我仍然对全局变量的工作方式感到有点困惑，因为它不符合我理解的语言语法。

还尝试了这些:

$-w = "hello"
#=> "hello"

$-a = "hello"
#=> NameError: $-a is a read-only variable

$-b = "hello"
#=> "hello"

$-ww = "hello"
#=> SyntaxError: unexpected tIDENTIFIER, expecting end-of-input
$-ww = "hello"
    ^

Answer 1

-w 是一个 Ruby 全局变量。

这是来自 documentation :

$-0 The alias to $/.

$-a True if option -a is set. Read-only variable.

$-d The alias of $DEBUG. See $DEBUG above for further discusison.

$-F The alias to $;.

$-i In in-place-edit mode, this variable holds the extension, otherwise nil.

$-I The alias to $:.

$-l True if option -l is set. Read-only variable.

$-p True if option -p is set. Read-only variable.

$-v An alias of $VERBOSE. See $VERBOSE above for further discussion.

$-w An alias of $VERBOSE. See $VERBOSE above for further discussion.