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Scripting & Automation Cheatsheet

A comprehensive cheat sheet covering essential scripting and automation concepts, tools, and techniques.

Scripting Fundamentals

Basic Concepts

Scripting: Writing a sequence of commands to automate tasks.
Automation: Using scripts and tools to perform tasks automatically, reducing manual intervention.
Key Benefits: Increased efficiency, reduced errors, and improved consistency.

Shebang: #! - Specifies the interpreter for the script (e.g., #!/bin/bash for Bash, #!/usr/bin/env python3 for Python).
Variables: Used to store and manipulate data.
Control Flow: Statements like if, else, for, and while to control the execution flow.

Functions: Reusable blocks of code to perform specific tasks.
Comments: # (Bash, Python, PowerShell) - Used to add explanatory notes to the code.

Scripting Languages

Bash

Primarily used for Unix-like operating systems. Great for system administration tasks.

Python

Versatile language suitable for web development, data analysis, and general-purpose scripting.

PowerShell

Designed for Windows system administration and automation. Includes powerful cmdlets.

Input/Output

Standard Input (stdin): Input from the keyboard or redirected from a file.
Standard Output (stdout): Output displayed on the screen or redirected to a file.
Standard Error (stderr): Error messages displayed on the screen or redirected to a file.

Redirection:

  • > Redirect stdout to a file (overwrites).
  • >> Redirect stdout to a file (appends).
  • 2> Redirect stderr to a file.
  • &> or 2>&1 Redirect both stdout and stderr to a file.

Piping:

  • | Connect the stdout of one command to the stdin of another.

Example: ls -l | grep 'myfile.txt'

Bash Scripting

Variables and Operators

Variable Assignment:

variable_name="value"

Example:
name="John"

Accessing Variables:

$variable_name or ${variable_name}

Example:
echo "Hello, $name!"

Arithmetic Operators:

+, -, *, /, %

Example:
result=$((5 + 3))
echo $result

String Operators:

= (equal), != (not equal), -z (empty), -n (not empty)

Example:
if [ "$name" = "John" ]; then echo "Match!"; fi

Control Structures

If Statement:

 
if [ condition ]; then
  # Code to execute if condition is true
elif [ condition2 ]; then
  # Code to execute if condition2 is true
else
  # Code to execute if all conditions are false
fi

For Loop:

 
for variable in list;
do
  # Code to execute for each item in the list
done

While Loop:

 
while [ condition ]; do
  # Code to execute while the condition is true
done

Functions

Function Definition:

 
function_name() {
  # Code to execute
  return value
}

Calling a Function:

function_name

Example:

greet() {
  echo "Hello, $1!"
}

greet "World"

Python Scripting

Basic Syntax

Variables:

variable_name = value

Example:
name = "Alice"

Data Types:

int, float, str, bool, list, tuple, dict

Example:
age = 30
price = 99.99

Operators:

+, -, *, /, %, ** (exponentiation), // (floor division)

Example:
result = 5 + 3

Comments:

# This is a comment

Control Flow

If Statement:

 
if condition:
  # Code to execute if condition is true
elif condition2:
  # Code to execute if condition2 is true
else:
  # Code to execute if all conditions are false

For Loop:

 
for variable in iterable:
  # Code to execute for each item in the iterable

While Loop:

 
while condition:
  # Code to execute while the condition is true

Functions

Function Definition:

 
def function_name(parameters):
  # Code to execute
  return value

Calling a Function:

function_name(arguments)

Example:

def greet(name):
  print(f"Hello, {name}!")

greet("World")

Modules

Importing Modules:
import module_name
from module_name import specific_item
import module_name as alias

Example:

import math
print(math.sqrt(16))

from datetime import datetime
print(datetime.now())

PowerShell Scripting

Basic Concepts

Cmdlets:

Commands in PowerShell (e.g., Get-Process, Write-Host).

Variables:

Start with a $ (e.g., $name = "John").

Piping:

Use | to pass objects between cmdlets (e.g., Get-Process | Where-Object {$_.CPU -gt 10}).

Variables and Data Types

Variable Assignment:

$variable_name = value

Example:
$name = "John"

Data Types:

[int], [string], [bool], [array], [hashtable]

Example:
[int]$age = 30

Arrays:

$myArray = @("item1", "item2", "item3")

Hashtables:

$myHash = @{Name="John"; Age=30}

Control Structures

If Statement:

 
if (condition) {
  # Code to execute if condition is true
} elseif (condition2) {
  # Code to execute if condition2 is true
} else {
  # Code to execute if all conditions are false
}

For Loop:

 
foreach ($item in $collection) {
  # Code to execute for each item in the collection
}

While Loop:

 
while (condition) {
  # Code to execute while the condition is true
}

Functions

Function Definition:

 
function function_name {
  param (
    $parameter1,
    $parameter2
  )
  # Code to execute
  return value
}

Calling a Function:

function_name -parameter1 value1 -parameter2 value2

Example:

function Greet {
  param (
    $Name
  )
  Write-Host "Hello, $Name!"
}

Greet -Name "World"
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