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env_variables.adoc

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Environment variables

An environment variable is a dynamic-named value that can affect the way running processes behave on a computer. In simple terms, it’s a variable whose value is set outside the program, usually in the operating system’s environment. These variables are part of the environment in which a process runs and can be accessed by any program running under that environment.

Environment variables are used for various purposes, including:

  • Configuration: They can be used to configure how software behaves. For example, setting the PATH variable in Unix-like systems specifies directories in which executable programs are located.

  • Customization: Users can set environment variables to customize their computing environment according to their preferences. This could include setting variables for default text editors, language preferences, or file system paths.

  • Inter-process Communication: Environment variables can be used by one process to communicate information to another process. For instance, a parent process might pass configuration information to a child process through environment variables.

  • Security: They can also play a role in security by controlling access to certain resources or features based on the value of specific variables.

  • Debugging and Development: Developers often use environment variables to configure development and debugging environments. They can control logging levels, debugging options, or enable/disable certain features during development.

Overall, environment variables provide a flexible and standardized way to configure and control the behavior of software and the operating system environment as a whole. They are an essential aspect of system configuration and software development.

Setting Up Environment Variables in Command Line

Windows

  1. Open Command Prompt:

    • Press Win + R to open the Run dialog.

    • Type cmd and press Enter.

  2. View Current Environment Variables:

    • To view all current environment variables, type set and press Enter.

  3. Set New Environment Variable:

    • To set a new environment variable, type: setx VARIABLE_NAME "variable_value" Replace VARIABLE_NAME with the name of your variable and "variable_value" with its value.

  4. Verify the Setting:

    • Close and reopen Command Prompt to ensure the changes take effect.

    • To verify, type echo %VARIABLE_NAME%. It should display the value you set.

macOS

  1. Open Terminal:

    • Use Spotlight (press Cmd + Space and type "Terminal") or go to Applications → Utilities → Terminal.

  2. View Current Environment Variables:

    • To view all current environment variables, type printenv and press Enter.

  3. Set New Environment Variable:

    • To set a new environment variable for the current session, type: export VARIABLE_NAME="variable_value" Replace VARIABLE_NAME with the name of your variable and "variable_value" with its value.

  4. Permanently Set Environment Variables (Optional):

    • To make the variable persist across sessions, add the export command to ~/.bash_profile or ~/.bashrc file.

Linux

  1. Open Terminal:

    • You can open the terminal using the shortcut Ctrl + Alt + T or search for it in your applications menu.

  2. View Current Environment Variables:

    • To view all current environment variables, type printenv and press Enter.

  3. Set New Environment Variable:

    • To set a new environment variable for the current session, type: export VARIABLE_NAME="variable_value" Replace VARIABLE_NAME with the name of your variable and "variable_value" with its value.

  4. Permanently Set Environment Variables (Optional):

    • To make the variable persist across sessions, add the export command to ~/.bash_profile or ~/.bashrc file.

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