#envvar #shell #bash #environment


Getting environment variables considering shell configuration

6 releases

0.1.5 Mar 6, 2023
0.1.4 Mar 6, 2023

#96 in Configuration

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envvars helps to detect a list of available shells and related environment variables. If works in two steps:

  • detecting a list of available shells and creating Profile for each found shell
  • loading a list of environment variables for selected or each shell


Getting all available (detected) shells and related to each shell list of environment variables

use envvars::{get_profiles, Profile};

let mut profiles: Vec<Profile> = get_profiles().unwrap();

// By default profile doesn't have loaded list of environment variables.
// It should be loaded calling method load().
profiles.iter_mut().for_each(|profile| {
    // Attempt to load envvars
    if let Err(err) = profile.load() {
        eprintln!("Cannot load envvars for {}: {err}", profile.name);
    if let Some(envvars) = &profile.envvars {
        println!("Environment variables for {}", profile.name);
        envvars.iter().for_each(|(key, value)| {
            println!("{key}: {value}");

Extract environment variables without shell context.

use std::collections::HashMap;
use envvars::get_context_envvars;

let vars: HashMap<String, String> = get_context_envvars().unwrap();

assert!(vars.contains_key("PATH") || vars.contains_key("Path") || vars.contains_key("path"));

Diffrence from std::env::vars

envvars actually executes each found shell it means: all settings of the target shell will be inited before a list of environment variables will be requested. That's very sensitive if the configuration of some shell includes some initialization script, which affects environment variables. That means in some cases std::env::vars and envvars could give different results.

How it works

Under the hood, envvars takes each shell, and executes it with a command, which posts a list of environment variables to stdout. As soon as executing is done, envvars reads stdout and parse environment variables into HashMap<String, String>.

As soon as extracting process could take a sensitive time (~1sec on windows and ~10ms on Unix-based OS), envvars doesn't extract environment variables during detecting the shell's profiles. That's the developer's decision when it should be done for the selected or each profile.

envvars creates a small executable application in the system's temporary folder. This application is used to "drop" list of environment variables into stdout of the parent process and does nothing else. As soon as envvars instance is dropped, the application would be removed from the disk.

For security reasons envvars checks the checksum of the extractor each time before using it. If a checksum is invalid (the file was damaged/changed etc), envars will remove a corrupted file and create a new one.

Unix specific

envvars reads /etc/shells and analyze each shell from a list

Windows specific

envvars checks for availability next shells:

  • Command Prompt
  • Windows PowerShell
  • .NET Core PowerShell Global Tool
  • Cygwin x64
  • Cygwin
  • bash (MSYS2)
  • GitBash

Guaranteed results

Because envvars tries to initialize each shell and "drop" a list of environment variables to stdout, the shell should support the possibility to put a command as an argument, for example: /bin/bash -c path_to_command. Obviously not many, but still some shells don't support it (like windows command prompt). In this case, you still can use get_context_envvars() to get a list of environment variables without the shell's context.


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