[Ruby] Ruby Variable Scope

Scope defines where in a program a variable is accessible. Ruby has four types of variable scope, local,global, instance and class. In addition, Ruby has one constant type. Each variable type is declared by using a special character at the start of the variable name as outlined in the following table.

Name Begins WithVariable Scope$A global variable@An instance variable[a-z] or _A local variable[A-Z]A constant@@A class variable

It is useful to know, however, that a number of pre-defined global variables are available to you as a Ruby developer to obtain information about the Ruby environment. A brief summary of each of these variables is contained in the following table.

Variable NameVariable Value$@The location of latest error$_The string last read by gets$.The line number last read by interpreter$&The string last matched by regexp$~The last regexp match, as an array of subexpressions$nThe nth subexpression in the last match (same as $~[n])$=The case-insensitivity flag$/The input record separator$\The output record separator$0The name of the ruby script file currently executing$*The command line arguments used to invoke the script$$The Ruby interpreter's process ID$?The exit status of last executed child process