I am developing an escript and want to return the code 1 to the shell in case of an error, so if my tool gets automated, the automation scripts can detect an error based on the returned code.
So, to keep it simply, we return right from the main function of my escript entrypoint module:
def main(_args) do
System.stop(1)
end
Then after I run my generated escript:
$ echo $?
0
Am I right that there should be a 1 instead of a 0?
So it may be a bug with escripts in Erlang/OTP? I would try to build a minimal erlang escript and see if you can reproduce it there. If so, that’s the bug. System.stop(1) is init:stop(1) in Erlang.
defmodule Excript.CLI do
def main(args \\ []) do
{opts, _, _} = OptionParser.parse(args, switches: [halt: :boolean])
if opts[:halt], do: System.halt(1), else: System.stop(1)
end
end
Ha, that’s a shame. I Just checked, System.halt(1) does work properly but it does not carefully shut down the VM. I assume it won’t cause any troubles in my case, but we can’t be sure about it.
Usually it is fine for escripts and sometimes even desired for faster shutdown. The difference is that System.halt() does not shutdown the applications supervision trees one by one. It just halts the system.
You can always manually shut down parts that need to be shut down cleanly before calling it though (just don’t shut down the kernel before you get a chance to call halt).