appenv ― per-application & per-directory shell environments

                __     _____   _____      __    ___   __  __
              /'__`\  /\ '__`\/\ '__`\  /'__`\/' _ `\/\ \/\ \
             /\ \L\.\_\ \ \L\ \ \ \L\ \/\  __//\ \/\ \ \ \_/ |
             \ \__/.\_\\ \ ,__/\ \ ,__/\ \____\ \_\ \_\ \___/
              \/__/\/_/ \ \ \/  \ \ \/  \/____/\/_/\/_/\/__/
                         \ \_\   \ \_\
                          \/_/    \/_/

appenv is a shell utility supporting bash and fish that allows you to update your shell environment on a per-application basis. It is similar in spirit to tools such as autoenv or direnv, and offers the following features:

• supports per-user (~/.appenv/) and per-directory (.appenv) environments
• init-style auto-loading of ~/.appenv/auto-NNN-*.appenv.sh files
• easily portable to other shells (fish, zsh, tcsh, xonsh, etc)
• nice API to set/append/prepend values to environment variables

$ mkdir dir ; echo "export PATH=`pwd`/dir" > dir/.appenv
$ cd dir
$ appenv
$ echo $PATH
/home/use/dir

appenv scripts should be written in bash, and do not have any specific requirement besides updating environment variables.

Here's a typical example:

#!/usr/bin/bash
if test -z $APP_EXAMPLE; then
	export APP_EXAMPLE=$HOME/.local/share/example
	export PATH=$APP_EXAMPLE/bin:$PATH
	export MANPATH=$APP_EXAMPLE/share/man:$MANPATH
fi

or using the appenv shell API functions:

appenv_declare APP_EXAMPLE $HOME/.local/share/example
appenv_prepend PATH        $APP_EXAMPLE/bin
appenv_prepend MANPATH     $APP_EXAMPLE/share/man
appenv_log     "Example environment loaded at $APP_EXAMPLE"

Installing

Download

appenv requires bash and python to run, both of these commands are likely already available. To automatically install appenv from github, do the following:

curl https://raw.githubusercontent.com/sebastien/appenv/master/install.sh | bash

this will install the appenv scripts under ~/.local/bin, you can also specify an alternative location by setting the APPENV_HOME variable before running the install script.

curl https://raw.githubusercontent.com/sebastien/appenv/master/install.sh\
| export APPENV_HOME=~/my-local/ && bash

alternatively, you can install from this repository:

git clone https://github.com/sebastien/appenv.git
cd appenv
bash install.sh

Shell configuration

To load these commands from your shell, do the following in bash (in your ~/.bashrc)

source ~/.local/bin/appenv.bash

in fish (in your ~/.config/fish/config.fish):

. ~/.local/bin/appenv.fish

Usage

System-wide environments

The typical usage would be to create an ~/.appenv directory and populate it with *.appenv.sh files, one for each application environment that you would like to be available.

Example:

/home/user/.appenv/
├── prod.appenv.sh
├── staging.appenv.sh
└── dev.appenv.sh

and then do

appenv dev

to load the ~/.append/dev.appenv.sh environment from anywhere on the filesystem.

It is also possible to prefix appenv script names with auto-NNN where NNN are digits. This features allows you to make the difference between scripts you can load on demand and those loaded automatically.

appenv-load ~/.appenv/auto-*.appenv.sh

The appenv-load command will be able to resolve auto-000-name.appenv.sh from just the name.

Directory-specific environments

Another usage is to create directory-specific environments, in which case you would add an .appenv file at the root of your project directory and then add appenv-autoload to your prompt in order to automatically load the .appenv when it is in scope.

$ cd myproject
$ cat <<EOT >> .appenv
appenv_declare MYPROJECT
appenv_prepend PATH $MYPROJECT/bin
appenv_prepend PYTHONPATH $MYPROJECT/lib/python
EOT
$ cd myproject
$ echo $MYPROJECT
[ blank ]
$ appenv
[ the content of the local .appenv file is sourced ]
$ echo $MYPROJECT
/home/user/myproject

Available commands

Once loaded in you shell, appenv offers the following commands:

• appenv-list DIR?

  lists the appenv scripts available in the current (or given) directory and all its ancestors.

• appenv(-autoload) DIR?

  automatically loads the .appenv file or the .append/*.appenv.sh files in the current (or given) directory, making sure the same environment is not loaded twice.

  Tip: execute appenv(-autoload) in your prompt to automatically load an environment on directory change.

• appenv-load FILE‥|NAME‥

  loads the application environment scripts(s) identified by the given NAME (resolved in ~/.appenv/<NAME>.appenv.sh) or FILE.

• appenv-unload FILE‥|NAME‥

  unloads a preset environment, reverting the changes made by appenv-load.

  Not implemented yet

• appenv-loaded

  lists the currently loaded appenv environments. These are also stored in $APPENV_LOADED

• appenv-locate NAME

  locates an environment file from appenv-list that is like NAME.appenv.sh, auto-*-NAME.appenv.sh or has a appenv_name declaration with the given NAME.

• appenv-export

  exports the current environment as a script that can be loaded to restore the environment to what it was.

  Not implemented yet

• appenv-import FILE?

  imports an environment saved from a previous export, if not FILE is given, will load the directives from stdin.

  Not implemented yet

• appenv-capture command

  captures the changes made to the environment of the given command, returning the update script in the same format as appenv-export.

  Not implemented yet

.appenv scripts API

Application environment scripts (*.appenv.sh) have the following API already available, defined in share/appenv/api.bash:

• appenv_module NAME VALUE?

  Declares a module with the given NAME and VALUE (optional). If the module is already defined, the appenv script will exit right away. This is a compbination of appenv_declare and appenv_name

   appenv_module developer-env
   # The following code will only be executed if MYAPP` is not defined.
   # The `MYAPP` variable will be set to `true` by default.
   ‥

• appenv_declare NAME VALUE?

  exits the script if the environment variable NAME is defined (and equal to VALUE if specified), effectively guarding the execution of the rest of the script if the variable has already been defined.

   appenv_declare MYAPP
   # The following code will only be executed if MYAPP` is not defined.
   # The `MYAPP` variable will be set to `true` by default.
   ‥

• appenv_name NAME

  sets a name for the init script that will be appended to the APPENV_STATUS variable.

  Tip: add $APPENV_STATUS to your right prompt and show which named environment are currenlty loaded.

• appenv_append NAME VALUE

  adds the given VALUE at the end of the given environment variable with the given NAME, ensuring that VALUE does not occurs twice.

   appenv_append PATH ~/.local/share/example/bin

• appenv_prepend NAME VALUE

  adds the given VALUE at the beginning of the given environment variable with the given NAME, ensuring that VALUE does not occurs twice.

   appenv_prepend PATH ~/.local/share/example/bin

• appenv_remove NAME VALUE

  removes the given VALUE from the given environment variable.

   appenv_remove PATH ~/.local/share/example/bin

• appenv_set NAME VALUE

  sets the given environment variable to the given VALUE

   appenv_set APP_EXAMPLE_HOME ~/.local/share/example

• appenv_load PATH

  loads the appenv file at the given $PATH

• appenv_clear NAME

  unsets the given environment variable

   appenv_clear APP_EXAMPLE_HOME
  

• appenv_post COMMAND

  sets a command that will be evaluated by the host shell once the appenv file is loaded.

   appenv nix-env
   appenv_post "nix-shell --command $APPENV_SHELL"
  

appenv also manages the following environment variables, which are defined while the script is being executed.

• APPENV_FILE

  The normalized path to the appenv file currently being loaded. This is only available from within *.appenv.sh or .appenv files.

• APPENV_DIR

  The dirname of APPENV_FILE

The following environment variables are defined when the script is executed and also automatically updated and exported:

• APPENV_LOADED

  The list of loadded scripts (by path), by colons :

• APPENV_STATUS

  The list of loaded named scripts (by name) separated by colons :

• APPENV_SHELL

  The host shell from which the appenv command was called.