From an included file, how can I get the filename of the file doing the including?

ruby

Solution

Your question stimulated me to crack open the Ruby interpreter source and see how `__FILE__` actually works. The answer is pretty interesting: it's implemented right inside the parser. The lexer has a special token type for `__FILE__`. When the parser sees that token, it converts it to a string constant, which contains the name of the file the parser is working on.

From line 14948 of ext/ripper/ripper.c:

case keyword__FILE__:
return NEW_STR(rb_external_str_new_with_enc(ruby_sourcefile, strlen(ruby_sourcefile),
                        rb_filesystem_encoding()));

I think this should make it clear that trying to make `__FILE__` return the name of the including file is completely impossible, unless you hack the Ruby interpreter source, or write your own preprocessor which transforms `__FILE__` to something else before passing the Ruby source to the interpreter!

Problem

Apologies for the poorly worded question title - no idea how to put it better! In the following code, when I execute `ruby bar.rb`, how can I make it output `bar.rb`, rather than `foo.rb`? In `foo.rb`: ``` module Foo def filename __FILE__ end end ``` In `bar.rb`: ``` require_relative 'foo' include Foo puts filename # outputs 'foo.rb' ``` This is for a library function that, each time some code is executed, records the location (and git ref) of that code.

Original source