EragonJ

$files          # 全域變數
@data           # 實體(Instance)變數
@@counter       # 類別(Class)變數
empty?          # A Boolean-valued method or predicate 
sort!           # An in-place alternative to the regular sort method 
timeout=        # A method invoked by assignment 

EragonJ

test = 1 
puts test.to_s
puts test.class

test = "xx"
puts test.to_s
puts test.class

#結果如下
#ruby test.rb

EragonJ

$                #全域(Global)變數
@                #實體(Instance)變數
[a-z] or _       #區域(Local)變數
[A-Z]            #常數(Constant)變數
@@               #類別(Class)變數

EragonJ

x = 10
=> 10
defined? x
=> "local-variable"

$x = 10
=> 10
defined? $x
=> "global-variable"

EragonJ

if windows 
  listcmd = 'dir' 
else 
  listcmd = 'ls' 
end 
listing = `#{listcmd}`

EragonJ

>> 5.times{ puts "test".object_id }                                     
85641038                                                                
85640870                                                                
85640702                                                                
85640534                                                                
85638980                                                                
=> 5  

EragonJ

?\t      # Character literal for the TAB character 
?\C-x    # Character literal for Ctrl-X 
?\111    # Literal for character whose encoding is 0111 (octal) 

x = ?\t
print x
=> 9

EragonJ

a = "hello "
a << "world"   #=> "hello world"
a.concat(33)   #=> "hello world!"

b = "hello "
b << "world"   #=> "hello world"

EragonJ

s = 'hello';   # Ruby 1.8 
s[0]           # 104: the ASCII character code for the first character 'h' 
s[s.length-1]  # 111: the character code of the last character 'o' 
s[-1]          # 111: another way of accessing the last character 
s[-2]          # 108: the second-to-last character 
s[-s.length]   # 104: another way of accessing the first character 
s[s.length]    # nil: there is no character at that index 
############################################################################
s = 'hello';   # Ruby 1.9 
s[0]           # 'h': the first character of the string, as a string 

EragonJ

s[0] = ?H        # 把第一個字元取代成 'H'
s[-1] = ?O       # 把最後一個字元取代成 '0'