[erlang-questions] Fwd: Report errors when using "-detached" option

Claes Wikström <>
Fri Nov 14 14:22:42 CET 2008


ERLANG wrote:
> Hi Michael,
> 
>> then I use application:start(sasl) in my program, and then use rb for
>> looking at all the reports (from an erl shell)
>>
> 
> That correct and my apps log everything too. But this will force you  
> to use "rb" to check the logs for errors (warnings or watherver).
> This is what I want to avoid.
> 
> The main idea here is to be able to return an exit code different from  
> 0 to notify
> the shell script that erlang app failed to load for some reason.

This is indeed a real problem. If daemon startup fails, you typically
want to indicate that through a call to exit(error_code) so that the
invoker can check $?


A tail-f we solved this by hacking the emulator startup a bit. I know
we sent those patches to otp, but I'm not sure if they were ever
incorporated.

You can also implement some sort of status checker in your program.
I a call that connects to the daemon and reports someting, thus startup
could be:

erl -detached ${flags}
erl -s mymod check_status
if [ ! $? = 0 ]; then
    echo "failed to start bla bla"
    exit 1
fi


/klacke



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