I use run_erl to start an erlang application, just like this
run_erl -daemon /tmp/erl_pipe /tmp/erl_log "erl -name 1#127.0.0.1 -setcookie 123456"
Then I Attach to erlang shell like this
to_erl /tmp/erl_pipe
And the question is, I used to quit erlang shell with 'ctrl + c', in this situation, 'ctrl+c' will quit the main node, I have seen my lead to ban this command by modify erlang/OTP source code, how to do that?
Start Erlang as erl +Bi. Note that you'll have to use init:stop() (shortcut q() in the shell) or halt() to stop the node if signals are ignored. Also, the Ctrl-G menu will not have the q option if you use this flag.
It is also possible to use +Bc, which makes Ctrl-C abort the current shell command instead of stopping the whole node. In this case, you can still use q from the Ctrl-G menu.
See http://erlang.org/doc/man/erl.html#emu_flags for the full documentation on runtime system flags.
I have a program that starts the application and then adds (children) workers to a supervisor. Obviously after doing only that it has nothing more left to do and it halts (exits). So making it not halt the VM would allow the workers to work.
The only solution I have came up was to add:
IO.gets "Working... To finish hit <Enter>."
at the end...
I want to build an escript that after running will not halt the Erlang VM just like:
elixir --no-halt -S mix run --eval 'MyApp.CLI.m
ain(["some-arg"])'
or
mix run --no-halt --eval 'MyApp.CLI.m
ain(["some-arg1,some-arg2"])'
Is there a way to do this with escript?
Or should I use a different solution to pack and distribute my program that is actually more like a server/daemon than a command line tool?
A typical approach to packaging such systems is an OTP release. You can use exrm for that.
If for some reasons, you still want to use escript, you can just call :timer.sleep(:infinity) after you start all the applications and processes.
NOTE: Starting from Elixir 1.9
We can use System.no_halt(true) to allow script to never stop.
Here is simple script example:
defmodule Mix.Tasks.NoHalt do
use Mix.Task
def run(_) do
System.no_halt(true)
IO.puts("Never die!")
end
end
This has been my current routine
sudo nohup erl -sname foo -pa ./ebin -run foo_supervisor shell -noshell -noinput &
where the shell function looks something like this
shell() ->
{ok, Pid} = supervisor:start_link({local,?MODULE}, ?MODULE, _Arg = []),
unlink(Pid).
If I don't unlink from shell it immediately stops for some reason. Is there a way I can just start my application like I would normally ie application:start(foo). Also what if I want to start sasl too? Also where could I learn more about making a self contained package using rebar?
Preface. About your unlink
In this other SO thread #filippo explains why you need the unlink when testing supervisors from the shell.
First. What you need is an Erlang application.
Reading from the doc:
In OTP, application denotes a
component implementing some specific
functionality, that can be started and
stopped as a unit, and which can be
re-used in other systems as well.
Details on how to implement an Erlang application are available here. The three main things you will need to do are:
Have a proper directory structure for your application
Write an application callback module implementing the Erlang application behaviour. That's where you will start your root supervisor
Provide an application resource file. This is where you tell the system - among other things - where to find your application callback module (look at the mod parameter).
Second. Starting SASL.
In the above application resource file, you can specify a list of applications you want to start before your application. You will add something like:
...
{applications, [kernel, stdlib, sasl]},
...
To tell it to start SASL.
Third. Rebar.
There's an introduction to Rebar here, which explains you how to use Rebar to help you in the above steps, to pack your brand new application into an Erlang release and how to start it.
I recently installed Erlang RFC4627 (JSON-RPC) with the debian package. I ran the test server using:
sudo erl -pa ebin
and then at the prompt:
test_jsonrpc:start_httpd().
returned
ok
I tested with http://:5671/ and got the success messages.
When I try to run rabbitmq-http2 however, I get the errors that the readme says are caused by rfc4627's code not being on the erlang search path. How do I put it on the path. I saw something on Dave Thomas's blog which suggested putting the path in the file:
~/.erlang
This didn't seem to work for me (maybe I did it wrong?).
The code module is how you manipulate the path within an application.
The flags -pa that you used in starting the Erlang shell actually refer to a function in this module:
add_patha(Dir) -> true | {error, What}
You are right about the .erlang file in your home directory - it is run at start-up time of the shell and you can add in handy paths.
For an application you can start the shell with a batch file that calls something like this:
erl -pa ./ebin ../../lib/some/path/ebin
The flags behaviour of erl is described here.
For more sophisticated path management you need to get familiar with how OTP release management is done (but I suspect that is a while away for you yet).
To start my program I do the next sequence:
$ erl
> c(module1).
> c(module2).
> c(modulen).
modulen:start().
Is there any possibility to create script that allow me to launch my program ?
You could use a loader script that takes care of starting your application in an OTP fashion:
-module(XYZ_app).
-export([start/0]).
start() ->
application:start(inets),
application:start(XYZ).
You launch that script through a shell script. Beware of using escript if you plan on building daemons running at the OS boot time as they are tricky.
#!/bin/bash
erl -boot start_sasl -s XYZ_app start
Of course you need your XYZ.app file (just an example):
{application, tinycouch,
[{description, "tinycouch"},
{vsn, "0.1"},
{modules, [
tinycouch, tinycouch_app, tinycouch_sup,
tinycouch_server, tinycouch_logger_h, tinycouch_utils,
tinycouch_db, mod_tinycouch
]},
{registered, [tinycouch
,tinycouch_server
,tinycouch_sup
]},
{applications, [kernel, stdlib, sasl, inets]},
{env, []},
%% Application Start point
{mod, {tinycouch_sup, []}}]}.
... and all your .erl files must have been compiled.
Note that if you intend to distribute your application (e.g. Debian repository etc), you probably should consider having a make file to compile and install your app.
As a final note: you could also go with a boot file (the ultimate OTP way) but I find those very constraining: a boot file ties your application to specific version release of Erlang (and other dependent applications). Your application might be able to run in various Erlang releases but you will need to have a separate build/release process for each "platform release" you intend to ship for.
You can compile the modules with erlc
erlc module1 module2 module3
You can also create a script to run you program
#!/usr/bin/escript
main(_) ->
modulen:start().
Then in the console:
chmod +x start.erl
./start.erl
Two ways
precompile your code
$ erlc module1.erl
$ erl -s module1 funcname arg1 arg2 ....
Or use escript
#!/usr/bin/env escript
main() ->
module1:fun(...)
escript is a scripting interface to Erlang
You can use erl -make directly, as it assumes all *.erl files should be compiled to *.beam, and skip it if they haven't been changed since last compile. Check out the make module for what you can put in your Emakefile to change certain behavior.
Using plain Makefile to invoke this compile strategy also gives other users a familiar build-procedure.
Having a bootstrap start function as jldupont suggests is a nice way to start up your development environment. It is even sufficiently fine for using in production to some point.
The next step is to use full OTP (*.rel) release files and generate boot scripts that starts all the applications in the order the *.app specify dependencies on each other.
In the home directory, create file
.erlang
in that file write
compile:file(/path-to/module1).
compile:file(/path-to/module2).
compile:file(/edit-real-path-to/modulen). % etcetera; do not use c(module) inside this file!
then, if you need add (inside .erlang):
module1:start(). % etc
When you run erl (in the shell), the content of the .erlang (provided this file is in the home dir) will be executed at start (of the interpreter-erlang-VM you launch).
You can create .erlang file in some other (some 'current') directory, then, if you run erl (erlang interpreter) in that directory, that another .erlang will override the content of that .erlang in the home dir (of that which is like /home/your-user-name/.erlang ).
It is good idea to write inside of .erlang some reminder, like
io:format(".erlang loaded-compiled module1!\n"). %etc
(as not to forget about that code which otherwise will be executed silently !)
(also, you can check, for this case, that e.g. module1 is indeed compiled and loaded after start, this or some similar way:
AllLoaded = code:all_loaded().
lists:filter(fun({Module,_})-> Module =:= module1 end, AllLoaded).
the answer should be like:
[{module1,"/home/your-user-name/(path-to-your-code)/module1.beam"}]
)
Check out Sinan and Faxien: http://www.erlware.org