erln8 (erl-in-ate) allows you to compile and manage multiple versions of Erlang from source. Instead of downloading individual source packages, it downloads the Github OTP mirror so you are essentially downloading all available versions at once :-) Additionaly, you can add your own git repos to support custom OTP patches etc.

The cool thing about erln8 is that you only need to add it to your PATH to use it. No funny environment tweaking ;-) It works by reading an erln8.config config file out of the current directory, or by searching up the directory tree until it finds one. This allows you to "set a version of Erlang to use for a project and forget it".

erln8 does not manage Erlang build dependencies. If you are using erln8, I'm assuming you are already capable enough to figure these out on your own.

• somewhat stable, I'm sure there are bugs.
• I'm still working on the test suite... in Ruby (hi haters!)

NOTE: erln8 version 0.9.0 breaks backwards compatibility. You'll need to rm -rf ~/.erln8.d and reinitialize erln8.

brew install https://raw.github.com/metadave/homebrew/erln8/Library/Formula/erln8.rb
 ## this will install the glib dependency if not already installed

See the Building section below to continue.

(Erlang + general erln8 deps)

sudo apt-get install build-essential libncurses5-dev openssl libssl-dev fop xsltproc unixodbc-dev libglib2.0-dev git autoconf

See the Building section below to continue.

(Erlang + general erln8 deps)

sudo yum install gcc glibc-devel make ncurses-devel openssl-devel autoconf glib2-devel.x86_64 git

this can be helpful as well:

yum groupinstall "Development tools"

See the Building section below to continue.

 # remove Erlang from your path!!

git clone https://github.com/metadave/erln8.git
cd erln8
make
sudo make install
 # the default location is /usr/local/bin/erln8
 # OR
sudo make PREFIX=/opt install

Running the tests requires Ruby 1.9.3 + iniparse (which is installed via bundle install).

cd test
bundle install
make

cd erln8
sudo make uninstall

• git
• glib-2.0
• gio-2.0

To create erln8 config files, clone the default OTP repo, and build the latest version of Erlang (OTP-17.0.1 as of writing), simply run:

erln8 --quickstart

Depending on your system, it could take quite awhile to download the OTP Git repository and build Erlang. It might be a nice time to get a beer/coffee/tea/Tab.

Note: there aren't any options passed to the configure script during build when --quickstart is used. On OSX, this defaults to a measly 32-bits install.

Once the quickstart completes, you'll still need to cd to a directory where you want to use Erlang and run:

erln8 --use quickstart_build

The quickstart will fail Erlang build dependencies aren't installed or correct. Once you have the required dependencies installed, you can continue the build with the following:

erln8 --build --tag OTP_R16B02 --id R16B02

*If you haven't added the erln8 directory to your path, do it now. If you already have Erlang in your path, REMOVE IT!

Run this once, it creates ~/.erln8.d and ~/.erln8.d/config

erln8 --init

Next, you'll need to clone the OTP source repo from Github if you don't have Erlang installed. This default repo is cloned to ~/.erln8.d/repos/default.

erln8 --clone default

To see a list of versions you can build, run:

erln8 --buildable

or

erln8 --buildable --repo default

replacing default with whatever erln8-configured Git repo you want to use.

If you already have Erlang installed, skip down to Linking an Existing Erlang below.

The following command will build Erlang R16B02 using the OTP_R16B02 tag from Git. This build can now be referred to by the --id value (see the erln8 --use example below). Also, see the ~/.erln8.d/config file for specific configs or add your own, or run erln8 --configs.

  erln8 --build --tag OTP_R16B02 --id r16b02 --config osx_llvm
  erln8 --build --tag OTP_R15B01 --id r15b01 --config osx_llvm

You can specify alternate Git repos to build from. erln8 --repos lists available repos or look in ~/.erln8.d/config

  erln8 --build --repo basho --tag OTP_R15B01 --id r15b01p --config osx_llvm

##Linking an existing version Erlang

If you already have a version of Erlang build at an alternate location, you can link erlang to it.

For example, I have an old copy of Erlang R14B04 located in /Users/dparfitt/erlang_R14B04, and I'd like to reference it by the ID R14B04:

erln8 --link /Users/dparfitt/erlang_R14B04 --id R14B04

You'll be able to run erln8 --list and see the linked version:

R16B02b3:slag:~$ erln8 --list
R16B02b3 -> /Users/dparfitt/.erln8.d/otps/R16B02b3
R16B02 -> /Users/dparfitt/.erln8.d/otps/R16B02
R14B04 -> /Users/dparfitt/.erln8.d/otps/R14B04

If I want to unlink this version of Erlang: version of Erlang:

NOTE: This does NOTE remove the Erlang directory that erln8 has linked to.

erln8 --unlink --id R14B04

at which point, R14B04 won't show up as a version of Erlang to use.

R16B02b3:slag:~$ erln8 --list
R16B02b3 -> /Users/dparfitt/.erln8.d/otps/R16B02b3
R16B02 -> /Users/dparfitt/.erln8.d/otps/R16B02

To see which versions of Erlang are available for use from erln8, run:

  erln8 --list

For any directory that has an Erlang project, you can run erln8 with the --use option to mark that directory and all subdirectories to use a specific version of Erlang WHENEVER YOU CD INTO THAT DIRECTORY.

 erln8 --use r16b02

If you need to change the version of Erlang that's already been configured for the current directory:

 erln8 --use r16b01 --force

If you want to find out which version of Erlang the cwd is using,

erln8 --show

This command simply creates an erln8.config file in the cwd. You can even edit it by hand to specify the configured version of Erlang by id, or just rerun erln8 --use some_other_version to change the value.

[0]:prime:~$ cat erln8.config
[Config]
Erlang=r16b02

erln8 provides shell completion for commands, available Erlang installations, and buildable Erlang installation.

source ~/path_to_erln8/bash_completion/erln8

If you installed on OSX via Brew (above), bash_completion is installed automatically for you.

A section titled SystemRoots can be created and maintained inside of ~/.erln8.d/config to specify versions of Erlang to use outside of $HOME. This can be useful if you don't have write access to these directories.

[SystemRoots]
/opt/foo=R16B01
/tmp=R15B01p

NOTE: a SystemRoot setting will NOT follow symlinks. On OSX, /tmp (among other paths) is actually a symlink to /private/tmp. Thanks Apple!

Simply run erln8 from your home directory with a version of Erlang that you'd like to use elsewhere.

NOTE: if you are building/running Erlang source from outside of your home directory, you'll need to run erln8 at a location higher up the directory tree.

you can specify a system default in ~/.erln8.d/config:

[Erln8]
system_default=R16B02

Note, the ID that is specified (R16B02 in this example) must have already been built or linked to erln8.

To get the latest OTP tags/branchs, you'll need to issue a fetch:

erln8 --fetch default

where default is the repo name. If you have multiple repositories configured, you'll need to issue fetch once per repo.

• Don't customize your prompt until you have erln8 fully installed.

The --prompt parameter displays the configured version of Erlang for the current working directory.

erln8 --prompt

For example, if you are using bash, you could add the following snippet to your .bash_profile:

function erl_version() {
  erln8 --prompt
}

 # note, this also displays git info for the cwd
PS1='\[$(tput bold)\]\[$(tput setaf 2)\]$(erl_version)\[$(tput sgr0)\]:\[\e[0;36m\]$(__git_ps1 "[%s]")\[\e[m\]\[$(tput setaf 3)\]\h\[$(tput sgr0)\]:\w\$ '; [[ $EUID == 0 ]] &&
PS1='\[$(tput bold)\]\[$(tput setaf 2)\]$(erl_version)\[$(tput sgr0)\]:\[\e[0;36m\]$(__git_ps1 "[%s]")\[\e[m\]\[$(tput setaf 3)\]\h\[$(tput sgr0)\]:\w\$ '

erln8 allows you to pass arbitrary flags to the configure script as part of a config. To add a config, edit ~/.erln8.d/config and append a name=configstring to the [Configs] section.

[Configs]
osx_llvm=--disable-hipe --enable-smp-support --enable-threads --enable-kernel-poll --enable-darwin-64bit

To specify environment variables to be used during a build, create a config name=configstring as show above, as well as an additional name_env=vars setting. Any config that has an accompanying *

[Configs]
osx_gcc=--disable-hipe --enable-smp-support --enable-threads --enable-kernel-poll --enable-darwin-64bit
osx_gcc_env=CC=gcc-4.2 CPPFLAGS='-DNDEBUG' MAKEFLAGS='-j 3'

If --config isn't specified as a parameter to a --build, erln8 will use the default_config config variable specified in the Erln8 section of ~/.erln8.d/config. This is simply the name of a config as configured above.

[Erln8]
default_config=default

For example, if --config isn't specified as a parameter to a --build, the config osx_llvm will be used:

[Erln8]
default_config=osx_llvm

• comments begin with the # character and may appear anywhere in the file
• all keys and values are case sensitive

####See also:

0. https://developer.gnome.org/glib/2.38/glib-Key-value-file-parser.html
1. http://freedesktop.org/wiki/Specifications/desktop-entry-spec/

To disable the erln8 startup banner, change the appropriate config settings located in the [Erln8] section of ~/.erln8.d/config. Boolean values are either true or false, and are case sensitive.

• banner

  • Show the version of Erlang that erln8 is running upon startup
  • true or false

• color

  • true or false

[Erln8]
banner=false
color=false

When erln8 is compiled, a single binary named erln8 is built and installed by default to /usr/local/bin. Additionally, symbolic links to all the Erlang commands in a typical distribution are created but linked to the single erln8 binary and are placed in /usr/local/bin. Thus, you have something like this:

$ ls -latr
-rwxr-xr-x    1 root      admin    36256 Dec 27 17:51 erln8
lrwxr-xr-x    1 root      admin       20 Dec 27 17:51 erlexec -> /usr/local/bin/erln8
lrwxr-xr-x    1 root      admin       20 Dec 27 17:51 erlc -> /usr/local/bin/erln8
lrwxr-xr-x    1 root      admin       20 Dec 27 17:51 erl_call -> /usr/local/bin/erln8
lrwxr-xr-x    1 root      admin       20 Dec 27 17:51 erl.src -> /usr/local/bin/erln8
lrwxr-xr-x    1 root      admin       20 Dec 27 17:51 erl -> /usr/local/bin/erln8
lrwxr-xr-x    1 root      admin       20 Dec 27 17:51 epmd -> /usr/local/bin/erln8
…

In this setup, whenever you call an Erlang command, you are really calling the erln8 command.

When erln8 starts, it checks argv[0] to see if it was called via a symlink (one of the erl, erlc, dialyzer, etc commands). If it was, it searches the current working directory for an erln8.config file. If one isn't found, it cd's up a directory and looks for an erln8.config file again. This continues until either an erln8.config file is found or the search reaches /. If an erln8.config file hasn't been found and / has been reached, the user hasn't configured a version of Erlang to use. Display an error and exit. Otherwise, use the version of Erlang specified in the erln8.config file and execv() that binary. execv() replaces the current process with the new process (see the man page for execv). So, a call to erlc will start up erln8 via symlink, but the erln8 process will be replaced during the execv() by the command located in the specified version of Erlang.

There is another layer of indirection as located in the ~/.erln8.d/otps/MY_OTP directory (with MY_OTP being a configured Erlang ID). This layer of indirection was added to take the legwork out of finding versioned binaries in the Erlang distribution. For example, the to_erl symlink points to ./dist/lib/erlang/erts-5.10.3/bin/to_erl. erln8 only needs to know the command name to run it, without having to know the version # of erts.

R16B02:slag:~/.erln8.d/otps/R16B02$ ls -latr
total 296
drwxr-xr-x   4 dparfitt  staff   136 Dec 23 10:43 dist
drwx------   3 dparfitt  staff   102 Dec 23 10:43 ..
lrwxr-xr-x   1 dparfitt  staff    71 Dec 23 10:43 xml_from_edoc.escript -> ./dist/lib/erlang/lib/erl_docgen-0.3.4.1/priv/bin/xml_from_edoc.escript
lrwxr-xr-x   1 dparfitt  staff    39 Dec 23 10:43 typer -> ./dist/lib/erlang/erts-5.10.3/bin/typer
lrwxr-xr-x   1 dparfitt  staff    40 Dec 23 10:43 to_erl -> ./dist/lib/erlang/erts-5.10.3/bin/to_erl
lrwxr-xr-x   1 dparfitt  staff    60 Dec 23 10:43 start_webtool -> ./dist/lib/erlang/lib/webtool-0.8.9.2/priv/bin/start_webtool
...

The .dist directory defined for each version of Erlang installed also allows erln8 to generate this list of symlinks for a linked version of Erlang (see above). Symlinks don't need to be placed in the linked directory (which could be anywhere in the filesystem).

#Contributing

Fork this repo, create a feature branch using something like this:

git checkout -b branch_name

and submit a pull request.

Please send me an email (dparfitt at basho dot com) and let me know if you want to work on any features.

Only friendly pull requests accepted.

#License

http://www.apache.org/licenses/LICENSE-2.0.html

© 2014 Dave Parfitt