[erlang-questions] How to capture all output to console during Common Test?

[Max Lapshin]

Hi.

I'm running ct_run  and want somehow to capture all output made to console (io:format,  ct:print).  Is it possible?

[Fred Hebert]

I ended up doing this for rebar3 through the cth_readable library. The
only practical way I found to hijack all traffic was to use a parse
transform to replace the function and tunnel it through my own.

Here's the parse transform I used for ct:pal/2-3 :
https://github.com/ferd/cth_readable/blob/master/src/cth_readable_transform.erl

https://github.com/ferd/cth_readable/blob/master/src/cth_readable_failonly.erl
shows how I got to capture and redirect most of lager and error_logger's
traffic as well, but it's fairly messy.

Regards,
Fred.
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[Vladimir Gordeev]

Well, it's possible to start your own Erlang IO server, start it in ct hook during init, and then make it as a group leader for root ct process.

http://erlang.org/doc/apps/stdlib/io_protocol.html

So just start your own process that handles io_reply, io_request, and then

erlang:group_leader(MyCustomIOServerPid, CtRootPid),

[Marco Molteni]

On 9 Jun 2017, at 18:06, Max Lapshin <max.l...@gmail.com> wrote:

> I'm running ct_run and want somehow to capture all output made to console (io:format, ct:print). Is it possible?

I wrote mock_io [1] to capture/inject I/O for EUnit. If it doesn't work out of the box with CT, it should be easy to adapt, I'll be happy to accept patches :-)

marco

[1] https://github.com/marco-m/mock_io

[PAILLEAU Eric]

>
Hi max,

you may have a look to io_server/0 and io_server/1 in
https://github.com/erlang/otp/blob/master/lib/observer/src/observer_procinfo.erl

was done to catch 'rb' output in observer.

cheers

[Max Lapshin]

On Sat, Jun 10, 2017 at 10:14 AM, Vladimir Gordeev <gordeev.v...@gmail.com> wrote:

Well, it's possible to start your own Erlang IO server, start it in ct hook during init, and then make it as a group leader for root ct process.

http://erlang.org/doc/apps/stdlib/io_protocol.html

So just start your own process that handles io_reply, io_request, and then

erlang:group_leader(MyCustomIOServerPid, CtRootPid),

Have you tried to do it?

[Vladimir Gordeev]

> Have you tried to do it?

Yeah, I captured by such manner all IO from custom erlang shell that I started by shell:start/2.
I didn't tried to do it with Common Test though.

Here is module of my own IO server process, just for example: https://gist.github.com/vladimir-vg/ab5a2096759e24e8f6d51386f043430e