[erlang-questions] Application can not be started

[T Ty]

To add to what Jay wrote:  it is common to have a dummy_proj.erl implement
the Application behaviour and have a start/0 function just for starting it
from the Unix/Windows command line.

When using rebar it creates dummy_proj_app.erl and you have 2 choices:

1. put a start/0 in dummpy_proj_app which means you can now do

      erl -pa apps/ebin/ -boot start_sasl -s dummy_proj_app

 or

2. rename dummy_proj_app.erl to dummy_proj.erl, put a start/0 in it and
change the dummy_proj.app.src file to match.

Either way your start/0 function must exist somewhere.




On Wed, Oct 22, 2014 at 10:51 PM, Jay Doane <jay@REDACTED> wrote:

> Here's a quote from the docs that T Ty mentioned:
>
> *-s Mod [Func [Arg1, Arg2, ...]](init flag)*
>
> Makes init call the specified function. Func defaults to start. If no
> arguments are provided, the function is assumed to be of arity 0. Otherwise
> it is assumed to be of arity 1, taking the list [Arg1,Arg2,...] as
> argument. All arguments are passed as atoms. See init(3)
> <http://erlang.org/doc/man/init.html>.
> So when you pass -s application ensure_all_started dummy_proj
> to erl, it's going to call application:ensure_all_started([dummy_proj])
> (note that the argument is a single element list), which is not what you
> want.
>
> I struggled with the best way to deal with this for a while, and
> eventually created a little helper module that looks like this:
>
> -module(app).
>
> %% @doc Allow applications to be started from command line: -s app start
> application-name
>
> -export([start/1]).
>
> start([App]) ->
>    application:start(App).
>
> and seems to work well enough for my purposes. You will want to either
> change the last line to application:ensure_all_started(App), or create a
> separate function that calls ensure_all_started. YMMV.
>
>
>
> On Wed, Oct 22, 2014 at 10:32 AM, 张国富 <cleancode@REDACTED> wrote:
>
>> Thanks, it is very helpful.
>> Now I added a module dummy_proj and the start function is implemented,
>> finally it's working by
>> $ erl -pa apps/ebin/ -boot start_sasl -s dummy_proj
>>
>> But personally I do not want to add a entire new module just for this
>> purpose, So I tried something else.
>> However, another problem shows up, that when I start erl shell by
>> $ erl -pa apps/ebin/ -boot start_sasl -s application start dummy_proj
>> or
>> $ erl -pa apps/ebin/ -boot start_sasl -s application ensure_all_started
>> dummy_proj
>> Nothing will go wrong but application dummy_proj will not be started at
>> the same time.
>> On the other hand, if I try
>> $ erl -pa apps/ebin/ -boot start_sasl -s appmon start
>> the AppMon tool will be started as expected.
>>
>> That's to say the application:start(dummy_proj) was called, but nothing
>> happened.
>> It's weird.
>>
>> Best wishes.
>> zhangguofu (Gary)
>>
>> 在 2014-10-22 15:13:24，"T Ty" <tty.erlang@REDACTED> 写道：
>>
>> According to the Erlang documentation
>>
>> http://erlang.org/doc/man/erl.html when you call
>>
>>     erl -s module
>>
>> And no other arguments provided it defaults to Func "start" and if no
>> arguments are provided, the function is assumed to be of arity 0.
>>
>> On Tue, Oct 21, 2014 at 11:48 PM, Jay Doane <jay@REDACTED> wrote:
>>
>>> I believe this line
>>>
>>> {"init terminating in do_boot",{undef,[{dummy_proj,
>>> start,[],[]},{init,start_it,1,[]},{init,start_em,1,[]}]}}
>>>
>>> indicates that the function start/0 is not defined in module dummy_proj,
>>> so if you want to start it like that on the command line, you could try
>>> adding something like the following to dummy_proj.erl:
>>> -export([start/1]).
>>> start() ->
>>>     application:ensure_all_started(dummy_proj).
>>>
>>>
>>> On Tue, Oct 21, 2014 at 1:33 PM, 张国富 <cleancode@REDACTED> wrote:
>>>
>>>> Hello all,
>>>> I'm now following a Erlang rebar tutorial at
>>>> http://www.metabrew.com/article/erlang-rebar-tutorial-generating-releases-upgrades,
>>>> the test application can be started inside the erlang shell, like
>>>> $ erl -pa apps/ebin/ -boot start_sasl
>>>> 1> application:start(dummy_proj).
>>>> =PROGRESS REPORT==== 21-Oct-2014::21:16:13 ===
>>>>          application: dummy_proj
>>>>           started_at: nonode@REDACTED
>>>> ok
>>>> 2> dummy_proj_server:poke().
>>>> {ok,1}
>>>> but it can not be started this way
>>>> $ erl -pa apps/ebin/ -boot start_sasl -s dummy_proj
>>>> Erlang R16B03 (erts-5.10.4) [source] [smp:4:4] [async-threads:10]
>>>> [kernel-poll:false]
>>>> .... <skip> .....
>>>> =PROGRESS REPORT==== 21-Oct-2014::21:17:23 ===
>>>>          application: sasl
>>>>           started_at: nonode@REDACTED
>>>> {"init terminating in
>>>> do_boot",{undef,[{dummy_proj,start,[],[]},{init,start_it,1,[]},{init,start_em,1,[]}]}}
>>>> Crash dump was written to: erl_crash.dump
>>>> init terminating in do_boot ()
>>>>
>>>> It seems Erlang is trying to call dummy_proj:start(), but I can not
>>>> understand why.
>>>> Anybody who ever encountered the same problem here? How can I make it
>>>> work?
>>>>
>>>> Thanks.
>>>>
>>>> Best wishes
>>>>
>>>> zhangguofu(Gary)
>>>>
>>>>
>>>>
>>>>
>>>>
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