[erlang-questions] Erlang term to ASCII

Bob Ippolito <>
Fri Feb 7 20:16:49 CET 2014


How is this other system maintaining the deeply-nested Erlang structure?
How or why is it in text? How does it get rendered without newlines and
indentation? Why not use a more predictable (less flexible) serialization
format (erlang term format, JSON, protocol buffers, …)?

I do not think that this is the best approach. There are many possible
representations of various tokens as Erlang source code and I would never
trust two implementations to render it exactly the same way unless I wrote
both of them. Some tokens that are going to be particularly problematic are
lists of integers (which may or may not be rendered like strings, with
various ways to escape), binaries (which may be rendered like strings or
not), and floating point numbers.




On Fri, Feb 7, 2014 at 10:17 AM, Brandon Clark <>wrote:

> I have 2 production systems, one Erlang and one not, both maintaining
> copies of a large, deeply-nested Erlang data structure.  I need to set up a
> monitoring script to confirm that both systems are holding identical copies
> of the data structure.
>
> The non-Erlang system is holding an ASCII rendering of the data structure.
>  Computing an MD5 sum of this string is easy.  If I can get the Erlang
> system to convert its data structure to a string, I can have it compute an
> MD5 sum as well and the monitoring is simply a matter of comparing hashes.
>
> I'm stuck on the process of converting the Erlang term to a string.
>
> Str = io_lib:format("~p", [Data])
>
> gives me what I want, except that it includes newlines and indentation
> that I can't expect the non-Erlang system to have.
>
> Str = io_lib:format("~w", [Data])
>
> eliminates the newlines and indentation but renders the textual components
> of Data as lists of integers, guaranteeing the result won't match the
> non-Erlang system.
>
> So the question is, how do I get a "~p"-style rendering of an
> arbitrarily-large Erlang term *without* newlines and indentation?
>
> Thank you!
>
> ~Brandon Clark
>
>
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