How to check env variables?

Checking environment variables is a fundamental task for understanding system configurations, troubleshooting applications, and verifying development setups. These variables store crucial information that processes and programs use to function correctly.

Checking Environment Variables on Windows

On Windows, there are several straightforward ways to inspect environment variables, depending on whether you want to view a specific variable or list all of them.

1. Using Command Prompt (CMD)

This method is quick and effective for both specific and general checks.

• To check a specific environment variable:

  1. Open the Command Prompt. You can do this by typing cmd in the Start menu search bar and pressing Enter.
  2. In the command window, type echo %VARIABLE_NAME% and press Enter. Replace VARIABLE_NAME with the actual name of the environment variable you want to check (e.g., echo %PATH% or echo %NUKE_DISK_CACHE%).
  3. The value of the variable, if set, will be displayed. If it's not set, it will typically echo the variable name itself (e.g., %NUKE_DISK_CACHE%) or nothing, depending on the shell configuration.

• To list all environment variables:

  1. Open the Command Prompt.
  2. Type set and press Enter.
  3. This command will display a comprehensive list of all environment variables currently set for your user session, including both user-specific and system-wide variables.

2. Using PowerShell

PowerShell offers similar functionality to CMD, with some object-oriented advantages.

• To check a specific environment variable:

  1. Open PowerShell (search for PowerShell in the Start menu).
  2. Type $env:VARIABLE_NAME and press Enter (e.g., $env:PATH or $env:TEMP).
  3. The value of the variable will be displayed.

• To list all environment variables:

  1. Open PowerShell.
  2. Type Get-ChildItem Env: or Get-Item Env: and press Enter.
  3. This will list all environment variables along with their values. You can pipe this to Format-Table or Format-List for better readability.

3. Using the Graphical User Interface (GUI)

The System Properties window allows you to view and modify environment variables through a user-friendly interface.

1. Right-click on the Start button and select System (or search for "Environment Variables" in the Start menu).
2. In the System window, click on Advanced system settings on the right or bottom.
3. In the System Properties dialog, navigate to the Advanced tab and click the Environment Variables... button.
4. Here, you will see two sections: User variables for [Your Username] and System variables. You can select any variable from these lists to view or edit its value.

Checking Environment Variables on Linux and macOS

Unix-like systems (Linux, macOS) provide powerful command-line tools for managing environment variables.

1. To check a specific environment variable:

• Open a terminal window.
• Type echo $VARIABLE_NAME and press Enter (e.g., echo $PATH or echo $HOME).
• The value of the variable will be printed to the console. If the variable is not set, this command will typically output an empty line.

2. To list all environment variables:

Multiple commands can be used, each with slight differences in scope:

• env:

  • This command lists all environment variables that are set for the current shell session. It typically shows variables that are inherited by child processes.
  • Usage: env

• printenv:

  • Similar to env, printenv displays all environment variables. You can also use it to check a specific variable by providing its name (e.g., printenv PATH).
  • Usage: printenv

• declare -x (Bash/Zsh):

  • This command, specific to Bash and Zsh shells, lists all exported shell variables, which include environment variables. It also shows shell functions that are exported.
  • Usage: declare -x

• set:

  • The set command (without arguments) lists all shell variables, including environment variables, local variables, and shell functions. This can be a very long list.
  • Usage: set

Summary Table

Operating System	Action	Command/Method	Description
Windows	Check specific variable	echo %VARIABLE_NAME% (CMD) / $env:VARIABLE_NAME (PowerShell)	Displays the value of a single environment variable.
Windows	List all variables	set (CMD) / Get-ChildItem Env: (PowerShell)	Shows all environment variables for the current session.
Windows	GUI Method	System Properties > Environment Variables	View and modify variables through a graphical interface.
Linux/macOS	Check specific variable	echo $VARIABLE_NAME	Displays the value of a single environment variable.
Linux/macOS	List all variables	env / printenv / declare -x	Shows all environment variables for the current session.

Understanding how to check environment variables is crucial for debugging application issues, configuring software, and ensuring your system behaves as expected.