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I have Erlang application's beam files which I want to decompile.

Application is Compiled and build with 'debug_info' options. here is snippet of emake file to which is used to build application :

{"apps/my_app/src/*",   [debug_info, nowarn_export_all, {outdir, "apps/my_app/ebin"},{pa, "deps"},{parse_transform, lager_transform}, {parse_transform, events_transform}]}.

I have tried function from beam_lib module but getting following Error :

1>{ok,{_,[{abstract_code,{_,AC}}]}} = beam_lib:chunks(abc,[abstract_code]).
** exception error: no match of right hand side value {error,beam_lib,{not_a_beam_file,'abc.beam'}}

I have also tried solution mentioned in following post Decompile erlang .beam files compiled without debug_info but Its not working for me. I'm getting following error :

1> file:write_file("/tmp/my_module_disasm", io_lib:fwrite("~p.\n", [beam_disasm:file(abc)])).
ok

/tmp/my_module_disasm file contains :

{error,beam_lib,{not_a_beam_file,'abc.beam'}}.

Anyone have Idea ?

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1 Answer 1

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Have you tried using recon:source/1? I think it does exactly what you need. If you don't want to use it, at least you can get inspiration from its source code:

-spec source(module()) -> iolist().
source(Module) ->
    Path = code:which(Module),
    {ok,{_,[{abstract_code,{_,AC}}]}} = beam_lib:chunks(Path, [abstract_code]),
    erl_prettypr:format(erl_syntax:form_list(AC)).
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16
  • I had already tried it, you can see it in code snippets in post.
    – parmar7725274
    Commented Oct 31, 2017 at 3:11
  • Looks like your module (abc) is not compiled. What does code:which(abc). return?
    – Brujo Benavides
    Commented Nov 1, 2017 at 21:10
  • I have taken backup from live node. So I don’t think so it is not compiled. And code:which(abc) is returning absolute path of beam file.
    – parmar7725274
    Commented Nov 2, 2017 at 6:02
  • Actually, on closer look, the error you're seeing comes from here, which means your file doesn't start with something like FOR1____BEAM (i.e. something that matches <<"FOR1", _Size:32, "BEAM">>. Out of curiosity, can you show me the first 12 bytes of your abc.beam file?
    – Brujo Benavides
    Commented Nov 2, 2017 at 12:48
  • here it is : <<69,82,76,50,62,12,178,214,62,207,41,11>> Or in printable format <<"ERL2>\f\262\326>\317)\v">>.
    – parmar7725274
    Commented Nov 2, 2017 at 15:13

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