envprobe 1.0

Overlaying pluggable environment setter: modules reimagined + toggleable direnv on the shell, rather than the directory level.

Envprobe

Envprobe (envprobe) is a shell hook tool that helps you manage your environment variables on a per-shell basis easily. There is no need for clunky export sequences or manual source-ing of who-knows-where hand-written script files.

Envprobe was originally conceived as the tool between shell modules and direnv, but with added features such as saving your configuration on the fly.

• The full documentation is available on Read the Docs.
• Installation
  • Dependencies
  • Download
  • Hook
• Quick user guide
  • Managing environment variables
  • Saved snapshots
  • Type-safe access
• Configuring variable handling
  • Obtaining variable type descriptions

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Installation

Dependencies

Envprobe is supplied as a no-tools-needed Python package. The only things you need to have installed on the system are one of our supported POSIX-compliant shells and Python 3.

Supported shells are reasonably modern versions of Bash and Zsh.

Officially supported configurations

These are the configurations that the CI is running tests on:

Operating system	Required dependencies	Shells supported
Ubuntu 18.04 LTS (Bionic Beaver)	Python ≥ 3.6	Bash (≥ 4.4), Zsh (≥ 5.4)
Ubuntu 20.04 LTS (Focal Fossa)	Python ≥ 3.8	Bash (≥ 5.0), Zsh (≥ 5.8)

Download

You can download Envprobe's official releases from PyPI.

pip install envprobe

From GitHub

You can also download Envprobe from the GitHub repository, either via git or in a tarball form. Download the project anywhere you please, and extract the archive. In this example, we'll use ~/envprobe as the location.

git clone http://github.com/whisperity/envprobe.git ~/envprobe \
    --origin upstream --single-branch --branch master --depth 1

or

mkdir ~/envprobe
wget http://github.com/whisperity/envprobe/tarball/master -O envprobe.tar.gz
tar xzf envprobe.tar.gz --strip-components=1 -C ~/envprobe/

Hook

Envprobe applies the changes to your environment variable every time a prompt is generated in your shell. For this to work, a hook must be set up in each shell you're using.

The easiest way to do this is to add the hook script at the end of the configuration file for your respective shell.

:warning: Note! If you are using other custom shell extensions, it is well-advised for the best experience to load Envprobe last.

Shell	Configuration file (usually)	Code to add
Bash	~/.bashrc	eval "$(envprobe config hook bash $$)";
Zsh (stock)	~/.zshrc	eval "$(envprobe config hook zsh $$)";
Zsh (Oh My Zsh)	~/.oh-my-zsh/custom/zzzzzz_envprobe.zsh (new file!)	eval "$(envprobe config hook zsh $$)";

Quick user guide

If Envprobe is successfully installed and hooked, the ep/envprobe and epc/envprobe-config convenience functions will be defined in the current shell. If you see something like below, the tool is good to go.

$ ep
usage: envprobe [-h] ...

The following guide will show the usage of Envprobe through a few practical examples.

For a complete overview on the commands available and their usage, you can always call ep -h (or ep get -h, etc. for each subcommand) to get a quick help. The complete documentation for the user-facing commands is available behind the link.

Managing environment variables

For easy access, the environment variable managing commands are also offered as shortcuts.

Command	Shortcut	Usage
get VARIABLE	?VARIABLE, or simply VARIABLE	Print the value of VARIABLE.
set VARIABLE VALUE	!VARIABLE, VARIABLE=VALUE	Sets VARIABLE to VALUE.
undefine VARIABLE	^VARIABLE	Undefine VARIABLE.
add VARIABLE VALUE	+VARIABLE VALUE (front), VARIABLE+ VALUE (back)	Add a VALUE to an array.
remove VARIABLE VALUE	-VARIABLE VALUE	Remove VALUE from an array.

$ ep get USER
USER=root

$ ep USER
USER=root

$ ep PATH
PATH=/usr/local/bin:/usr/bin:/sbin:/bin

$ echo $SOME_VARIABLE
# No result, variable is not defined.
$ ep SOME_VARIABLE=MyValue
$ echo $SOME_VARIABLE
MyValue

$ ep ^SOME_VARIABLE
$ echo $SOME_VARIABLE
# No result.



$ fancy
fancy: command not found!

$ ep +PATH /opt/fancy/bin
$ fancy
Fancy tool works!

$ ep PATH
PATH=/opt/fancy/bin:/usr/local/bin:/usr/bin:/sbin:/bin

$ pwd
/root

$ ep -PATH /opt/fancy/bin
$ ep PATH+ .
$ ep PATH
PATH=/usr/local/bin:/usr/bin:/sbin:/bin:/root

$ ep +PATH ..
PATH=/:/usr/local/bin:/usr/bin:/sbin:/bin:/root

Saved snapshots

For easy access, some of the snapshot management commands are also offered as shortcuts.

Command	Shortcut	Usage
diff [var1 var2...]	% [var1 var2...]	Show the difference between the current environment and the last saved one (optionally only for the variables named).
save [--patch] SNAPSHOT [var1 var2...]	}SNAPSHOT [-p] [var1 var2...]	Save the changes (optionally of only the variables named) to the snapshot named SNAPSHOT. If -p is given, ask for confirmation of each individual change.
load [--patch] SNAPSHOT [var1 var2...]	{SNAPSHOT [-p] [var1 var2...]	Load the changes (optionally to only the variables names) from the snapshot named SNAPSHOT. If -p is given, ask for confirmation of each individual change.
list		List the saved snapshots' names.
delete SNAPSHOT		Delete the snapshot named SNAPSHOT.

$ ep %
# (No output, initially the environment hasn't been changed yet.)

$ ep PATH
PATH=/usr/local/bin:/usr/bin/:/sbin:/bin

$ ep SOME_VARIABLE=foo
$ ep +PATH /tmp
$ ep -PATH /sbin
$ ep PATH+ /home/user/bin

$ ep %
(+) Added:       SOME_VARIABLE
        defined value: foo

(!) Changed:     PATH
        added:         /tmp
        added:         /home/user/bin
        removed:       /sbin

$ ep } mypath PATH
For variable 'PATH' the element '/tmp' was added.
For variable 'PATH' the element '/home/user/bin' was added.
For variable 'PATH' the element '/sbin' was removed.

$ ep } other_vars -p
New variable 'SOME_VARIABLE' with value 'foo'.
Save this change? (y/N) _



$ ep list
mypath
other_vars

$ ep delete mypath
$ ep list
other_var



$ ep load custompaths
For variable 'PATH' the element '/srv/custom/bin' will be added.

$ ep PATH
PATH=/srv/custom/bin:/tmp:/home/user/bin

$ ep { foobar -n
New variable 'FOO' will be created with value 'bar'.

$ ep FOO
FOO is not defined

$ ep { foobar -p
New variable 'FOO' will be created with value 'bar'.
Load and apply this change? (y/N) _

Saved snapshots

Envprobe offers type safety when accessing environment variables, such as prohibiting assigning a textual value to a _PID variable. The type of a variable is decided based on several heuristics by default, and can be configured by the user.

$ echo $SSH_AGENT_PID
12345

$ export SSH_AGENT_PID="invalid-value"
# The above example works, even though a "_PID" variable should only
# contain numbers.

$ ep SSH_AGENT_PID=98765
$ ep SSH_AGENT_PID="foo"
[ERROR] Failed to execute: could not convert string to number.

$ ep SSH_AGENT_PID
SSH_AGENT_PID=98765

Configuring variable handling

The envprobe-config (or epc) command contains various subcommands that can be used to configure Envprobe's behaviour.

For a complete overview on the commands available and their usage, you can always call epc -h (or epc track -h, etc. for each subcommand) to get a quick help. The complete documentation for the user-facing commands is available behind the link.

Command	Usage
hook ...	Generate the Shell hook that allows Envprobe to interface with the environment.
set VARIABLE ...	Set additional information, such as a description, for a variable.
track VARIABLE	Configure whether changes to a VARIABLE should be managed in saved snapshots.
descriptions update	Download the variable descriptions to use locally.

Obtaining variable type descriptions

Envprobe is managed with a sister project, the Envprobe Variable Descriptions Knowledge Base which contains a curated list of environment variable descriptions and types. This database is used together with other heuristics to provide type-safe access to variables. The description of a variable, when queried, may come from a local copy of this database too. Read more about this feature.

To initially download, or subsequently update, the description database, execute:

epc descriptions update