irb(main):006:0> $_
=> nil
irb(main):007:0> gets
foobar
=> "foobar\n"
irb(main):008:0> $_
=> "foobar\n"

irb(main):002:0> $&
=> nil
irb(main):010:0> /(foo)(bar)(BAZ)?/ =~ "foobarbaz"
=> 0
irb(main):011:0> $&
=> "foobar"

irb(main):012:0> $~
=> #<MatchData "foobar" 1:"foo" 2:"bar" 3:nil>

irb(main):026:0> $1
=> "foo"
irb(main):027:0> $~[1]
=> "foo"

irb(main):016:0> $`
=> ""  #由于最后匹配成功的内容是foobar，输入的字符串前面没有别的字符所以是""

irb(main):028:0> $'
=> "baz"

irb(main):029:0> $+
=> "bar"

irb(main):030:0> $1
=> "foo"
irb(main):031:0> $2
=> "bar"
irb(main):032:0> $3
=> nil

def exception
    begin
        raise "exception test."
    ensure
        puts $!
    end
end

exception

def exception
    begin
        raise "exception test."
    ensure
        puts $@
        puts "$@ size is:#{[email protected]}"
    end
end

exception

irb(main):076:0> $/  #初始的输入分割符
=> "\n"
irb(main):077:0> gets
=> "\n"
irb(main):078:0> "test" #输入回车之后，默认插入"\n"，输入结束
=> "test"
irb(main):079:0> $/="@" #修改输入符为"@"
=> "@"
irb(main):080:0> gets   #输入回车之后没有结束读取进程，直到输入"@"之后结束
test
@
=> "test\n@"

irb(main):082:0> print "abc"
abc=> nil
irb(main):083:0> $\="@"
=> "@"
irb(main):084:0> print "abc"
abc@=> nil

irb(main):087:0> ["a","b","c"].join
=> "abc"
irb(main):088:0> $,=","  #修改切分字符为","
=> ","
irb(main):089:0> ["a","b","c"].join #输出结果改变
=> "a,b,c"
irb(main):090:0> 

irb(main):090:0> $; 
=> nil
irb(main):091:0> "abc".split  #默认的切分字符情况下，把整个字符当成一个元素
=> ["abc"]
irb(main):092:0> $;="b"
=> "b"
irb(main):093:0> "abc".split #以"b"为切分字符情况下，把整个字符当成两个元素
=> ["a", "c"]

irb(main):094:0> $$
=> 5167

irb(main):095:0> $:
=> ["/usr/local/lib/site_ruby/1.8", "/usr/local/lib/site_ruby/1.8/i486-linux", "/usr/local/lib/site_ruby/1.8/i386-linux", "/usr/local/lib/site_ruby", "/usr/lib/ruby/vendor_ruby/1.8", "/usr/lib/ruby/vendor_ruby/1.8/i486-linux", "/usr/lib/ruby/vendor_ruby", "/usr/lib/ruby/1.8", "/usr/lib/ruby/1.8/i486-linux", "/usr/lib/ruby/1.8/i386-linux", "."]

irb(main):096:0> $LOAD_PATH
=> ["/usr/local/lib/site_ruby/1.8", "/usr/local/lib/site_ruby/1.8/i486-linux", "/usr/local/lib/site_ruby/1.8/i386-linux", "/usr/local/lib/site_ruby", "/usr/lib/ruby/vendor_ruby/1.8", "/usr/lib/ruby/vendor_ruby/1.8/i486-linux", "/usr/lib/ruby/vendor_ruby", "/usr/lib/ruby/1.8", "/usr/lib/ruby/1.8/i486-linux", "/usr/lib/ruby/1.8/i386-linux", "."]