add env-vars documentation

environment_variables_guide.md

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+# Environment Variables and rcfiles Guide
+
+## Environment Variables Overview
+
+Environment variables are dynamic-named values that affect the processes running on an operating system. They are used to store configuration settings, paths, and other important information. Here's a step-by-step guide on how to work with environment variables.
+
+## 1. Setting Environment Variables:
+
+### On Linux/Mac
+
+**Temporary (for the current session):**
+
+```bash
+export VARIABLE_NAME=value
+```
+
+**Permanent (across sessions):**
+Add the export command to your shell profile file (e.g., ~/.bashrc, ~/.zshrc).
+
+```bash
+echo 'export VARIABLE_NAME=value' >> ~/.bashrc
+source ~/.bashrc
+```
+
+### On Windows
+
+**Temporary (for the current session):**
+
+```powershell
+$env:VARIABLE_NAME = "value"
+```
+
+**Permanent (across sessions):**
+Use the System Properties window to set user or system environment variables.
+
+## 2. Using Environment Variables in rcfiles:
+
+### Example: Bash Shell (~/.bashrc or ~/.bash_profile)
+
+```bash
+# Example: Adding a custom directory to the PATH
+export PATH=$PATH:/path/to/custom/directory
+
+# Example: Setting a default editor
+export EDITOR=vim
+```
+
+### Example: PowerShell Profile ($PROFILE)
+
+```powershell
+# Example: Adding a custom directory to the PATH
+$env:PATH += ";C:\path\to\custom\directory"
+
+# Example: Setting a default editor
+$env:EDITOR = "notepad.exe"
+```
+
+## 3. Common Configurations:
+
+### Node.js Development
+
+```bash
+export NODE_ENV=development
+export PORT=3000
+```
+
+### Python Development
+
+```bash
+export PYTHONPATH=/path/to/project
+export FLASK_ENV=development
+```
+
+## 4. Windows Considerations:
+
+**On Windows, environment variables can be set through the System Properties or using PowerShell.**
+**To persistently modify environment variables on Windows, use the [System Properties](https://www.computerhope.com/issues/ch000549.htm) window. This requires administrative privileges.**
+
+## 5. Security Considerations:
+
+**Avoid storing sensitive information directly in environment variables.**
+**On Windows, be cautious about using environment variables in scripts as they can be easily accessed.**
+
+## 6. Best Practices:
+
+**Use uppercase letters and underscores for variable names (e.g., DATABASE_URL).**
+**Document your environment variables in a README file for better collaboration.**
+
+By following these steps and examples, you can effectively manage and use environment variables in various scenarios, making your development environment more flexible and scalable.