在Ruby编程语言中，$的名称是什么：

Question

我想知道更多关于$:的知识，但我不知道如何调用。

:015 > $: 
=> ["/Users/Nerian/.rvm/rubies/ruby-1.9.3-rc1/lib/ruby/site_ruby/1.9.1", 
"/Users/Nerian/.rvm/rubies/ruby-1.9.3-rc1/lib/ruby/site_ruby/1.9.1/x86_64-darwin11.1.0", 
"/Users/Nerian/.rvm/rubies/ruby-1.9.3-rc1/lib/ruby/site_ruby", 
"/Users/Nerian/.rvm/rubies/ruby-1.9.3-rc1/lib/ruby/vendor_ruby/1.9.1", 
"/Users/Nerian/.rvm/rubies/ruby-1.9.3-rc1/lib/ruby/vendor_ruby/1.9.1/x86_64-darwin11.1.0", 
"/Users/Nerian/.rvm/rubies/ruby-1.9.3-rc1/lib/ruby/vendor_ruby", 
"/Users/Nerian/.rvm/rubies/ruby-1.9.3-rc1/lib/ruby/1.9.1", 
"/Users/Nerian/.rvm/rubies/ruby-1.9.3-rc1/lib/ruby/1.9.1/x86_64-darwin11.1.0"] 

• 这样做有什么名字？
• 如何以及何时使用？
• 是否应该使用它，这是一种好的做法还是不好的做法？
• 是否支持所有Ruby实现？
• 有关它的任何文档？

Answer 1

• 的$:全球的规范（英文）名称为$LOAD_PATH。
• 正如其名说，它是库搜索路径的阵列，即，表示所有文件夹的字符串的数组，其中解释器将搜索库（当它遇到一个require "mylibrary"指令）
• 它可与使用在处理全局变量时必须小心谨慎。实际上，在编写包含在宝石或库中的测试或演示脚本时，经常会使用它，以便测试修改加载路径，以便在安装之前查找待测试库（例如，$: << "../lib"，假设脚本位于同级lib）
• 它被所有规范的Ruby版本/实现使用。请注意，当前目录.是1.8.x上的$：的一部分，并且出于安全原因已在1.9.x上删除。
• Docs在每个Ruby引擎上都可用（picaxe book，ruby docs站点）。

Answer 2

这相当于$LOAD_PATH。所以我想你可以称之为“加载路径”。谷歌ruby load_path，你应该找到很多有用的信息。

Personnaly我更喜欢读$LOAD_PATH，但$:是语言的一部分，所以我想可以使用它。

Answer 3

红宝石有一些预先定义的变量

Pre-defined variables 
$!   The exception information message set by 'raise'. 
$@   Array of backtrace of the last exception thrown. 
$&   The string matched by the last successful match. 
$`   The string to the left of the last successful match. 
$'   The string to the right of the last successful match. 
$+   The highest group matched by the last successful match. 
$1   The Nth group of the last successful match. May be > 1. 
$~   The information about the last match in the current scope. 
$=   The flag for case insensitive, nil by default. 
$/   The input record separator, newline by default. 
$\   The output record separator for the print and IO#write. Default is nil. 
$,   The output field separator for the print and Array#join. 
$;   The default separator for String#split. 
$.   The current input line number of the last file that was read. 
$<   The virtual concatenation file of the files given on command line (or from $stdin if no files were given). 
$>   The default output for print, printf. $stdout by default. 
$_   The last input line of string by gets or readline. 
$0   Contains the name of the script being executed. May be assignable. 
$*   Command line arguments given for the script sans args. 
$$   The process number of the Ruby running this script. 
$?   The status of the last executed child process. 
$:   Load path for scripts and binary modules by load or require. 
$"   The array contains the module names loaded by require. 
$DEBUG  The status of the -d switch. 
$FILENAME Current input file from $<. Same as $<.filename. 
$LOAD_PATH The alias to the $:. 
$stderr The current standard error output. 
$stdin  The current standard input. 
$stdout The current standard output. 
$VERBOSE The verbose flag, which is set by the -v switch. 
$-0  The alias to $/. 
$-a  True if option -a is set. Read-only variable. 
$-d  The alias to $DEBUG. 
$-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  The alias to $VERBOSE. 
$-w  True if option -w is set. 

http://www.zenspider.com/Languages/Ruby/QuickRef.html