Master Cloud Engineering & DevOps.

#!/usr/bin/env bash
set -euo pipefail   # exit on error, unset variable, or failed pipeline stage

echo "Script name: $0"
echo "First argument: $1"
echo "All arguments: $@"
echo "Argument count: $#"

name="Ada"
echo "$name"                 # always quote a variable reference
echo "${name:-Unknown}"       # default value if name is unset or empty
echo "${#name}"                # length of the string

readonly PI=3.14               # constant - reassigning it is an error
export PATH="$PATH:/opt/bin"   # visible to child processes too

if [[ "$name" == "Ada" ]]; then
  echo "Hello, Ada"
fi

if [ -f "$file" ]; then
  echo "$file exists"
fi

case "$1" in
  start) echo "starting" ;;
  stop)  echo "stopping" ;;
  *)     echo "usage: $0 start|stop" ;;
esac

for f in *.log; do
  echo "Found: $f"
done

while read -r line; do
  echo "Line: $line"
done < input.txt

greet() {
  local name="$1"     # local - doesn't leak into the caller's scope
  echo "Hi, $name"
}
greet "Ada"

x = 5                 # int
y = 3.14               # float
name = "Ada"           # str
is_valid = True        # bool
nothing = None         # NoneType

a, b = 1, 2            # multiple assignment
a, b = b, a             # swap without a temporary variable

nums = [1, 2, 3]
nums.append(4)          # [1, 2, 3, 4]
nums[0]                 # 1 (first item)
nums[-1]                # 4 (last item)
nums[1:3]                # [2, 3] (slice)

squares = [n * n for n in nums]   # list comprehension

person = {"name": "Ada", "age": 30}
person["age"]                   # 30
person.get("email", "n/a")       # "n/a" - no KeyError if missing
person["email"] = "ada@example.com"

unique = {1, 2, 2, 3}             # {1, 2, 3} - duplicates dropped
unique.add(4)

for n in [1, 2, 3]:
    print(n)

for i, n in enumerate(["a", "b"]):
    print(i, n)          # 0 a, then 1 b

n = 0
while n < 3:
    n += 1

def greet(name, greeting="Hello"):
    return f"{greeting}, {name}!"

def total(*args, **kwargs):
    return sum(args)

square = lambda x: x * x

class User:
    def __init__(self, name):
        self.name = name

    def greet(self):
        return f"Hi, {self.name}"

class Admin(User):
    def greet(self):
        return f"{super().greet()} (admin)"

try:
    result = 10 / 0
except ZeroDivisionError as e:
    print(f"Can't divide by zero: {e}")
finally:
    print("Always runs")

raise ValueError("Invalid input")