[erlang-questions] Re: how do I get escript to emit all output before exiting?

Mike Oxford moxford@REDACTED
Mon Apr 4 20:06:18 CEST 2011

What about having init:halt() send a sync'd message to the group leader to
shut down?
Once the group leader shuts down and returns then init:halt() will exit.
Even without a group-leader shutdown, even having the group-leader return a
ping-type message could unblock the init:halt() and ensure that you've
processed the messages at least that far, thus "flushing the buffer."


On Mon, Apr 4, 2011 at 10:24 AM, Scott Lystig Fritchie <
fritchie@REDACTED> wrote:

> Matthias Lang <matthias@REDACTED> wrote:
> ml> What IO situation is the code above trying to take care of? Why not
> ml> just
> ml> my_halt(Reason) ->
> ml>    init:stop(Reason),
> ml>    receive after infinity -> ok
> ml> end.
> ml> Not sure if this is a bug or if I'm just expecting too much, but
> ml> tossing output by default doesn't seem nice because it leads to code
> ml> that seems to work except when it doesn't.
> IIRC the stuff scribbled to the console via io:format() is actually done
> by sending messages to the group leader process.  You're at the
> scheduler's whim to decide whether the group leader gets executed &
> processes the I/O requests before the VM halts.
> Having said that, I've been bitten by this same concurrency feature.
> C/Ruby/Python folks don't expect the feature.  Even never-touched-
> another-language Erlang hackers may not expect it.  But short of having
> a function like like escript:halt/1 to take the place of your my_halt()
> function ... and a whole lot of doc additions to point out that calling
> io:format() is **not** a thin wrapper around the syscall/stdlib calls:
>    write(1, str, strlen(str));
>    /* OR */
>    fwrite(str, strlen(str), 1, stdout);
> ... I can't think of an easier fix.  (Perhaps I simply need more
> coffee?)
> -Scott
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