If you know about Ripper, you know that it’s a bridge between the ruby language parser and your own ruby app. It lets you parse ruby files just as ruby would see them. It’s currently marked as experimental, but its been in ruby since 1.9.
It’s quite hard going getting what you want out of it, one of the problems is the multiple arities of the events it produces. Another is its documentation, it’s really weak. Sven Fuchs wrote a pretty decent article to get you going.
In regards to the arities, you can discover the token<->event structure by firing up irb:
irb(main):001:0> require 'ripper.so' # To include the _TABLE constants
=> true
irb(main):002:0> require 'awesome_print' # for awesome output
=> true
irb(main):010:0> ap({ scanner: Ripper::SCANNER_EVENT_TABLE, parser: Ripper::PARSER_EVENT_TABLE })
{ :scanner => {
:CHAR => 1,
:__end__ => 1,
:backref => 1,
:backtick => 1,
:comma => 1,
:comment => 1,
:const => 1,
:cvar => 1,
:embdoc => 1,
:embdoc_beg => 1,
:embdoc_end => 1,
:embexpr_beg => 1,
:embexpr_end => 1,
:embvar => 1,
:float => 1,
:gvar => 1,
:heredoc_beg => 1,
:heredoc_end => 1,
:ident => 1,
:ignored_nl => 1,
:int => 1,
:ivar => 1,
:kw => 1,
:label => 1,
:lbrace => 1,
:lbracket => 1,
:lparen => 1,
:nl => 1,
:op => 1,
:period => 1,
:qsymbols_beg => 1,
:qwords_beg => 1,
:rbrace => 1,
:rbracket => 1,
:regexp_beg => 1,
:regexp_end => 1,
:rparen => 1,
:semicolon => 1,
:sp => 1,
:symbeg => 1,
:symbols_beg => 1,
:tlambda => 1,
:tlambeg => 1,
:tstring_beg => 1,
:tstring_content => 1,
:tstring_end => 1,
:words_beg => 1,
:words_sep => 1},
:parser => {
:BEGIN => 1,
:END => 1,
:alias => 2,
:alias_error => 1,
:aref => 2,
:aref_field => 2,
:arg_ambiguous => 0,
:arg_paren => 1,
:args_add => 2,
:args_add_block => 2,
:args_add_star => 2,
:args_new => 0,
:array => 1,
:assign => 2,
:assign_error => 1,
:assoc_new => 2,
:assoc_splat => 1,
:assoclist_from_args =>gt; 1,
:bare_assoc_hash => 1,
:begin => 1,
:binary => 3,
:block_var => 2,
:block_var_add_block => 2,
:block_var_add_star => 2,
:blockarg => 1,
:bodystmt => 4,
:brace_block => 2,
:break => 1,
:call => 3,
:case => 2,
:class => 3,
:class_name_error => 1,
:command => 2,
:command_call => 4,
:const_path_field => 2,
:const_path_ref => 2,
:const_ref => 1,
:def => 3,
:defined => 1,
:defs => 5,
:do_block => 2,
:dot2 => 2,
:dot3 => 2,
:dyna_symbol => 1,
:else => 1,
:elsif => 3,
:ensure => 1,
:excessed_comma => 1,
:fcall => 1,
:field => 3,
:for => 3,
:hash => 1,
:if => 3,
:if_mod => 2,
:ifop => 3,
:lambda => 2,
:magic_comment => 2,
:massign => 2,
:method_add_arg => 2,
:method_add_block => 2,
:mlhs_add => 2,
:mlhs_add_star => 2,
:mlhs_new => 0,
:mlhs_paren => 1,
:module => 2,
:mrhs_add => 2,
:mrhs_add_star => 2,
:mrhs_new => 0,
:mrhs_new_from_args => 1,
:next => 1,
:opassign => 3,
:operator_ambiguous => 2,
:param_error => 1,
:params => 7,
:paren => 1,
:parse_error => 1,
:program => 1,
:qsymbols_add => 2,
:qsymbols_new => 0,
:qwords_add => 2,
:qwords_new => 0,
:redo => 0,
:regexp_add => 2,
:regexp_literal => 2,
:regexp_new => 0,
:rescue => 4,
:rescue_mod => 2,
:rest_param => 1,
:retry => 0,
:return => 1,
:return0 => 0,
:sclass => 2,
:stmts_add => 2,
:stmts_new => 0,
:string_add => 2,
:string_concat => 2,
:string_content => 0,
:string_dvar => 1,
:string_embexpr => 1,
:string_literal => 1,
:super => 1,
:symbol => 1,
:symbol_literal => 1,
:symbols_add => 2,
:symbols_new => 0,
:top_const_field => 1,
:top_const_ref => 1,
:unary => 2,
:undef => 1,
:unless => 3,
:unless_mod => 2,
:until => 2,
:until_mod => 2,
:var_alias => 2,
:var_field => 1,
:var_ref => 1,
:vcall => 1,
:void_stmt => 0,
:when => 3,
:while => 2,
:while_mod => 2,
:word_add => 2,
:word_new => 0,
:words_add => 2,
:words_new => 0,
:xstring_add => 2,
:xstring_literal => 1,
:xstring_new => 0,
:yield => 1,
:yield0 => 0,
:zsuper => 0}}
=> nil 
