Study Notes on Command Line and Scripting

Graphical User Interface (GUI): A user-friendly interface consisting of images and icons that can be clicked to perform actions. The purpose is to simplify interactions with the computer for the average user.
Command Line Interface (CLI): The underlying system that executes user commands entered textually.
- Even when using a GUI, the commands executed are still based on code.
- The CLI remains a powerful tool that is integrated into operating systems and provides a way to configure and manipulate the OS and applications installed on it.

Commands are similar in some ways to the syntax of object-oriented programming languages, but they serve a different purpose.
Scripting vs Programming:
- Scripting: Typically aimed at automation and executing repeatable tasks without complex software creation.
  - Motivated by the goal to automate redundant tasks that are executed manually.
- Programming: Writing detailed software applications to perform specific tasks.

Functions: A reusable block of code that can be invoked using a simple command or identifier.
- Example: A function ‘ping’ could replace 15 lines of code to perform a specific action.
- Commands evolved from these functions, creating a library of common commands for users to utilize.
- Execution of commands involves typing the command in the CLI and pressing enter, which launches the command and runs it.
- Sequence of commands is critical in scripting; order impacts execution.

To create a script, a user can take individual commands and write them in a text file with the proper file extension.
File Extension: Determines how the operating system handles the execution of the file.
- Example: Changing from .txt to .cmd converts a regular text file into an executable script file in Windows.
Example Script:
- A simple ping command saved as nettest.txt can verify whether a network card is functional by sending packets out and receiving them back.
Key Details:
- Executable scripts have their respective icons and are recognized by the OS to run in proper environments.

Batch Scripts: In Windows, commands can be written in .bat or .cmd files to automate processes.
PowerShell: A more advanced scripting language designed for system administrators. It is built into Windows and offers additional functionalities compared to batch scripts.
- Supports both administrative tasks and script automation across systems.
Bash: Popular in Linux environments, similar to PowerShell for Windows.

Compilation vs. Interpretation:
- Programs are compiled, meaning they are transformed into executable files which then run as software.
- Scripts are interpreted, executed line by line without previous compilation. This allows for real-time changes and debugging.
- Example of vulnerabilities in compiled programs: logic errors can result in detrimental outcomes, while scripts allow for more dynamic adjustments.
Resource Allocation:
- Scripts can be resource-intensive, leading to potential system slowdowns during execution. Task scheduling and running scripts during off-hours can optimize resource use.

Navigational Commands:
- cd: Change directory.
- dir: List directory contents.
- mkdir: Make a new directory.
File Management:
- del: Delete files.
- copy: Copy files and directories.
- move: Move or rename files.
- rmdir: Remove directories.
Administrative Commands:
- ping: Check connectivity by sending ICMP packets.
- ipconfig: Display network configuration of the system.
- netstat: Show active network connections and protocols.

Scripts are used to automate repetitive tasks which consume time and resources.
Scripts can be generalized to run across various systems by using variables, allowing for adaptability across different user environments.
Automation of tasks can increase productivity and efficiency within IT departments and system administration roles.

Environmental Variables: Predefined variables in the OS that hold essential information:
- Example: username holds the current user's name.
- Scripts can utilize these variables for uniform execution across systems without hard-coding values.

Common Commands in Linux:
- ls: List directory contents.
- rm: Remove files.
- cat: View text files.
- Manual Page Access: Use man command to access help documentation for different commands.
Pipe Command: Redirect output from one process to another.

The command line and scripting provide technical users with a robust and efficient means to perform administrative tasks and automate operations within both Windows and Linux environments.
Understanding the functionalities and differences between scripting and programming is essential for effective system management and administration.

Writing scripts allows for the automation of complex sequences of commands, streamlining operations, and avoiding repetitive manual tasks.
Understanding the way commands work, their syntax, and how to troubleshoot errors through effective scripting practices is key to efficiency in system administration operations.