https://github.com/boardwalk/erltest

Erlang example application
https://github.com/boardwalk/erltest

Last synced: 4 days ago
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Erlang example application

• Host: GitHub
• URL: https://github.com/boardwalk/erltest
• Owner: boardwalk
• Created: 2017-01-26T02:15:22.000Z (almost 8 years ago)
• Default Branch: master
• Last Pushed: 2017-01-26T04:56:30.000Z (almost 8 years ago)
• Last Synced: 2024-08-01T13:24:42.446Z (3 months ago)
• Language: Erlang
• Homepage:
• Size: 7.81 KB
• Stars: 3
• Watchers: 3
• Forks: 2
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

Awesome Lists containing this project

• awesome-ccamel - boardwalk/erltest - Erlang example application (Erlang)

README

        
# erltest

Erlang example application. I created this for myself to understand how an Erlang application goes together without Elixir's Mix doing everything for me.

## Directory structure

```

erltest/

  Our application's directory. This could also be called Name-VSN if we

  cared about versioning.

erltest/src/

  All of our Erlang source code.

erltest/src/myapp.erl

  Implements the application behavior. Starts a supervisor named 'mysuper'.

erltest/src/mysuper.erl

  Implements the supervisor behavior. Starts a child named 'myserver'.

erltest/src/myserver.erl

  Implements the gen_server behavior. Doesn't do anything except print on startup.

erltest/ebin/

  Compiled source code as .beam files and our .app file.

erltest/ebin/erltest.app

  Describes our application. The 'applications' key specifies what applications

  must be started before this one. The optional 'mod' key specifies what module

  implements the 'application' behavior to start and stop it.

erltest.rel

  Describes our release, including all of the applications it contains.

```

## Usage

To compile our source code, we run build-erl:

```

$ ./build-erl

```

This compiles `erltest/src/*.erl` to `erltest/ebin/*.beam`.

To create our boot file, we run build-boot:

```

$ ERL_LIBS=. ./build-boot

```

The creates erltest.script, a script that describes how to start our release as well as erltest.boot, a binary version of the script. We need `ERL_LIBS=.` because Erlang needs to be able to find the erltest.app file of the erltest application we referenced in erltest.rel, and the current directory is not in its load path by default.

To finally bring up our system, we run erl:

```

$ ERL_LIBS=. erl -boot erltest

Erlang/OTP 19 [erts-8.6] [source] [128-bit] [smp:32:32] [async-threads:10] [hipe] [kernel-poll:false] [dtrace]

myserver init

Eshell V8.6  (abort with ^G)

```

This time we need `ERL_LIBS=.` so Erlang can find our .beam files. `-boot erltest` tells Erlang to execute erltest.boot, which essentially starts the kernel, stdlib, and erltest applications.

Now we stop our application:

```

> application:stop(erltest).

myserver terminate

ok

=INFO REPORT==== 25-Jan-2027::20:47:00 ===

    application: erltest

    exited: stopped

    type: permanent

```

And restart it if we want:

```

> application:start(erltest).

myserver init

ok

```

We can see our supervisor and server running with i:

```

> i().

Pid                   Initial Call                          Heap     Reds Msgs

Registered            Current Function                     Stack              

...

<0.67.0>              supervisor:mysuper/1                   233       96    0

mysuper               gen_server:loop/6                        9              

<0.68.0>              myserver:init/1                        233       34    0

myserver              gen_server:loop/6                        9              

...

```

You can talk to the server too:

```

> gen_server:call(myserver, "jabba").

"hello jabba from myserver"

```

That's it! Not too bad.