水龟
即使使用用户提供的值也可以安全地运行Shell命令
用法
基本的，正常的东西：
line = Terrapin :: CommandLine . new ( "echo" , "hello 'world'" )
line . command # => "echo hello 'world'"
line . run # => "hello world\n"
内插参数：
line = Terrapin :: CommandLine . new ( "convert" , ":in -scale :resolution :out" )
line . command ( in : "omg.jpg" ,
resolution : "32x32" ,
out : "omg_thumb.jpg" )
# => "convert 'omg
