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

Scott Lystig Fritchie fritchie@REDACTED
Mon Apr 4 19:24:39 CEST 2011

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


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