[erlang-questions] Can werl be detached?

John Ashmun <>
Wed May 25 23:07:26 CEST 2016


That is indeed the knack I needed.

Thanks!

Sent from my iPhone

> On May 25, 2016, at 1:30 PM, Daniel Goertzen <> wrote:
> 
> I have a windows app (also on R15) and this is the shortcut that launches it:
> 
> Target: "C:\Program Files (x86)\myprogram\erlang\erts\bin\werl.exe" -detached -smp enable -run bootstrap"
> 
> Start in: "C:\Program Files (x86)\myprogram\erlang\erts\bin"
> 
> So, try changing the current directory first to erts/bin before running detached.
> 
> 
> 
>> On Tue, May 17, 2016 at 6:47 PM John R. Ashmun <> wrote:
>> Perhaps my subject is not quite the correct question.  Here's my context:
>> 
>> I'm beginning to recreate in Erlang on Microsoft Windows 10 a public domain program I used to enjoy on my Commodore Amiga:  mATC was a game in which the user acted as a military Air Traffic Controller.  I am using a wx window to draw the player's map with aircraft data blocks overlaid.  I don't have a use for the initial window that opens when werl is started.
>> 
>> http://erlang.org/doc/man/werl.html
>> 
>> says, in part, "All flags except -oldshell work as they do for the erl command."  I don't have a UNIX-y system available to me to learn how they work for the erl command.  (The erl command as an interactive program is iffy in a Windows Command Prompt window.)
>> 
>> In particular, the description of -detached in
>> 
>> http://erlang.org/doc/man/erl.html
>> 
>> would seem to be what I want:
>> 
>> "Starts the Erlang runtime system detached from the system console. Useful for running daemons and backgrounds processes. Implies -noinput."
>> 
>> I want the Erlang VM to run my game without an Erlang shell's having opened a window, and I want my game to be in control of its wx window.
>> 
>> Further, following what I think I learned from "Erlang and OTP in Action", I have an OTP application being started by a boot file created from a .rel file.  All of this is in the setting of an ancient Erlang release:  R15B.
>> 
>> If I use this Command Prompt batch file, mATC.bat:
>> 
>> werl -pa ebin -pa mATC_app\ebin -detached -boot mATC -config sys
>> 
>> a Windows error message window appears that says:
>> 
>> "Failed to execute C:\Program Files\erl5.9\erts5.9\bin\beam.smp.dll
>>  The system cannot find the file specified."
>> 
>> The DLL is actually present at that location, and of course everything runs well when I don't use -detached.
>> 
>> Please advise.
>> 
>> Regards,
>> John Ashmun
>> 
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>> 
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