Installing more than one version of Erlang/OTP on a machine - erlang

Question

Is this possible to have different versions of Erlang/OTP installed simultaneously on the same platform?

Answer 1

I use Kerl to install Erlang on my machines. Quite easy to use, and allows to have several Erlang systems installed on same machine. You can then easily choose the one you want to use.

Answer 2

It is no only possible, but also very frequent. On my machine I have one version that I installed for development (R13B03) it is the default version when I launch erl.
A second copy of the same version associated with nitrogen. this copy is used when I start my nitrogen website. The version will not change when I will use the R16B.. for development
A partial older version which came with the installation of Wings3D.

Answer 3

Yes, I usually install different versions in my home directory. I build them from source:
./configure --prefix=$HOME/r15b01
make && make install
Then I can choose a version to use with PATH=$HOME/r15b01/bin:$PATH, and compile and run things as usual.
These days I use asdf for this. Install asdf and add the relevant line to your .bashrc, and then run:
asdf plugin add erlang
asdf install erlang 22.3.3
asdf install erlang 23.0.2
Then you can set one of the Erlang versions you just built as the default version:
asdf global erlang 23.0.2
Or you can set it to be used in the current directory and its subdirectories - this will create a .tool-versions file in the current directory:
asdf local erlang 22.3.3

Answer 4

On a Mac, Macport helps switching, even between versions it covers and newer ones.
E.g. with Erlang 17 installed directly from Erlang Solutions, you could switch back to RB1603 (open a new terminal window afterwards):
sudo port activate erlang #R16B03-1_0+hipe+ssl
Switch back to Erlang 17 by _de_activating the Macports install (and open a new terminal window afterwards):
sudo port deactivate erlang #R16B03-1_0+hipe+ssl
List all versions you have installed with:
port installed erlang

Answer 5

Using the Nix package manager there is no need to globally install interpreters (especially because sometimes multiple versions are needed), and nix-shell will open up a sub-shell with the Erlang executable available in the path.
1. Getting only the Erlang (no shell.nix)
For the current version in the active channel:
nix-shell -p erlang
For other versions not in the current channel, a specific channel can be given:
nix-shell -I nixpkgs=channel:nixos-unstable -p erlangR22
Or add path to the Nix expression in your NixOS/nixpkgs clone:
$ nix-shell -I nixpkgs=~/clones/nixpkgs -p erlangR23
2. More elaborate project setup configurations: use a shell.nix file
A complex development environment can be spun up, and calling nix-shell shell.nix will take care of all - even automatically when entering a directory if set up with direnv(archived).
2.1 Examples
Erlang
This will drop you in a shell with erl and rebar3 available, along with the other programs specified in buildInputs.
{ pkgs ? import ~/clones/nixpkgs {} }:
pkgs.mkShell {
buildInputs = with pkgs; [
beam.packages.erlangR22.erlang
beam.packages.erlangR22.rebar3
curl
ffmpeg
git
google-cloud-sdk
jq
];
# Where would be the best place for this?
shellHook = ''
export ERL_AFLAGS="-kernel shell_history enabled"
'';
Elixir/Phoenix web project
This (archived) will set up an environment for an Elixir/Phoenix web app complete with a spun up PostgreSQL dev instance:
####################################################################
# Importing a cloned Nixpkgs repo (from my home directory), because
# the latest channels don't have Elixir 1.9.
# See https://nixos.org/nix/manual/#idm140737317975776 for the meaning
# of `<nixpkgs>` and `~` in Nix expressions (towards the end of that
# section).
####################################################################
{ pkgs ? import ~/clones/nixpkgs {} }:
pkgs.mkShell {
buildInputs = with pkgs; [
beam.packages.erlangR22.elixir_1_9
postgresql_11
nodejs-12_x
git
inotify-tools
];
shellHook = ''
####################################################################
# Create a diretory for the generated artifacts
####################################################################
mkdir .nix-shell
export NIX_SHELL_DIR=$PWD/.nix-shell
####################################################################
# Put the PostgreSQL databases in the project diretory.
####################################################################
export PGDATA=$NIX_SHELL_DIR/db
####################################################################
# Put any Mix-related data in the project directory
####################################################################
export MIX_HOME="$NIX_SHELL_DIR/.mix"
export MIX_ARCHIVES="$MIX_HOME/archives"
####################################################################
# Clean up after exiting the Nix shell using `trap`.
# ------------------------------------------------------------------
# Idea taken from
# https://unix.stackexchange.com/questions/464106/killing-background-processes-started-in-nix-shell
# and the answer provides a way more sophisticated solution.
#
# The main syntax is `trap ARG SIGNAL` where ARG are the commands to
# be executed when SIGNAL crops up. See `trap --help` for more.
####################################################################
trap \
"
######################################################
# Stop PostgreSQL
######################################################
pg_ctl -D $PGDATA stop
######################################################
# Delete `.nix-shell` directory
# ----------------------------------
# The first step is going back to the project root,
# otherwise `.nix-shell` won't get deleted. At least
# it didn't for me when exiting in a subdirectory.
######################################################
cd $PWD
rm -rf $NIX_SHELL_DIR
" \
EXIT
####################################################################
# If database is not initialized (i.e., $PGDATA directory does not
# exist), then set it up. Seems superfulous given the cleanup step
# above, but handy when one gets to force reboot the iron.
####################################################################
if ! test -d $PGDATA
then
######################################################
# Init PostgreSQL
######################################################
pg_ctl initdb -D $PGDATA
######################################################
# PORT ALREADY IN USE
######################################################
# If another `nix-shell` is running with a PostgreSQL
# instance, the logs will show complaints that the
# default port 5432 is already in use. Edit the line
# below with a different port number, uncomment it,
# and try again.
######################################################
# sed -i "s|^#port.*$|port = 5433|" $PGDATA/postgresql.conf
fi
####################################################################
# Start PostgreSQL
# ==================================================================
# Setting all necessary configuration options via `pg_ctl` (which
# is basically a wrapper around `postgres`) instead of editing
# `postgresql.conf` directly with `sed`. See docs:
#
# + https://www.postgresql.org/docs/current/app-pg-ctl.html
# + https://www.postgresql.org/docs/current/app-postgres.html
#
# See more on the caveats at
# https://discourse.nixos.org/t/how-to-configure-postgresql-declaratively-nixos-and-non-nixos/4063/1
# but recapping out of paranoia:
#
# > use `SHOW` commands to check the options because `postgres -C`
# > "_returns values from postgresql.conf_" (which is not changed by
# > supplying the configuration options on the command line) and
# > "_it does not reflect parameters supplied when the cluster was
# > started._"
#
# OPTION SUMMARY
# --------------------------------------------------------------------
#
# + `unix_socket_directories`
#
# > PostgreSQL will attempt to create a pidfile in
# > `/run/postgresql` by default, but it will fail as it
# > doesn't exist. By changing the configuration option
# > below, it will get created in $PGDATA.
#
# + `listen_addresses`
#
# > In tandem with edits in `pg_hba.conf` (see
# > `HOST_COMMON` below), it configures PostgreSQL to
# > allow remote connections (otherwise only `localhost`
# > will get authenticated and the rest of the traffic
# > discarded).
# >
# > NOTE: the edit to `pga_hba.conf` needs to come
# > **before** `pg_ctl start` (or the service
# > needs to be restarted otherwise), because then
# > the changes are not being reloaded.
# >
# > More info on setting up and troubleshooting remote
# > PosgreSQL connections (these are all mirrors of the
# > same text; again, paranoia):
# >
# > + https://stackoverflow.com/questions/24504680/connect-to-postgres-server-on-google-compute-engine
# > + https://stackoverflow.com/questions/47794979/connecting-to-postgres-server-on-google-compute-engine
# > + https://medium.com/scientific-breakthrough-of-the-afternoon/configure-postgresql-to-allow-remote-connections-af5a1a392a38
# > + https://gist.github.com/toraritte/f8c7fe001365c50294adfe8509080201#file-configure-postgres-to-allow-remote-connection-md
HOST_COMMON="host\s\+all\s\+all"
sed -i "s|^$HOST_COMMON.*127.*$|host all all 0.0.0.0/0 trust|" $PGDATA/pg_hba.conf
sed -i "s|^$HOST_COMMON.*::1.*$|host all all ::/0 trust|" $PGDATA/pg_hba.conf
# + `log*`
#
# > Setting up basic logging, to see remote connections
# > for example.
# >
# > See the docs for more:
# > https://www.postgresql.org/docs/current/runtime-config-logging.html
pg_ctl \
-D $PGDATA \
-l $PGDATA/postgres.log \
-o "-c unix_socket_directories='$PGDATA'" \
-o "-c listen_addresses='*'" \
-o "-c log_destination='stderr'" \
-o "-c logging_collector=on" \
-o "-c log_directory='log'" \
-o "-c log_filename='postgresql-%Y-%m-%d_%H%M%S.log'" \
-o "-c log_min_messages=info" \
-o "-c log_min_error_statement=info" \
-o "-c log_connections=on" \
start
####################################################################
# Install Node.js dependencies if not done yet.
####################################################################
if test -d "$PWD/assets/" && ! test -d "$PWD/assets/node_modules/"
then
(cd assets && npm install)
fi
####################################################################
# If $MIX_HOME doesn't exist, set it up.
####################################################################
if ! test -d $MIX_HOME
then
######################################################
# ... but first, test whether there is a `_backup`
# directory. Had issues with installing Hex on NixOS,
# and Hex and Phoenix can be copied from there, just
# in case.
######################################################
if test -d "$PWD/_backup"
then
cp -r _backup/.mix .nix-shell/
else
######################################################
# Install Hex and Phoenix via the network
######################################################
yes | mix local.hex
yes | mix archive.install hex phx_new
fi
fi
if test -f "mix.exs"
then
# These are not in the `if` section above, because of
# the `hex` install glitch, it could be that there is
# already a `$MIX_HOME` folder. See 2019-08-05_0553
mix deps.get
######################################################
# `ecto.setup` is defined in `mix.exs` by default when
# Phoenix project is generated via `mix phx.new`.
# It does `ecto.create`, `ecto.migrate`, and run
# `priv/seeds`.
######################################################
mix ecto.setup
fi
'';
####################################################################
# Without this, almost everything fails with locale issues when
# using `nix-shell --pure` (at least on NixOS).
# See
# + https://github.com/NixOS/nix/issues/318#issuecomment-52986702
# + http://lists.linuxfromscratch.org/pipermail/lfs-support/2004-June/023900.html
####################################################################
LOCALE_ARCHIVE = if pkgs.stdenv.isLinux then "${pkgs.glibcLocales}/lib/locale/locale-archive" else "";
}
How to find packages with attributes path on the console
$ nix-env -qaP 'erlang*'
# ...
nixos.erlangR20 erlang-20.3.8.9
nixos.erlangR21 erlang-21.3.8.3
nixos.erlang erlang-22.1.7
# ...
$ nix-env -f ~/clones/nixpkgs/ -qaP 'erlang*'
# ...
nixos.erlangR20 erlang-20.3.8.9
nixos.erlangR21 erlang-21.3.8.3
nixos.erlang erlang-22.1.7
# ...
=== >>> erlangR23 erlang-23.0.2 <<<====

Answer 6

Consider using kerl. It allows you to work with several Erlang installations https://github.com/kerl/kerl