if [[ "$status" == "active" ]]; then
    echo "Service is running"
elif [[ "$status" == "stopped" ]]; then
    echo "Service is stopped"
else
    echo "Unknown status: $status"
fi

if [[ condition ]]; then command; fi

if [[ condition ]]
then
    command
fi

# File checks
[[ -f "$config" ]] || die "Config not found: $config"
[[ -d "$output_dir" ]] || mkdir -p "$output_dir"

# String checks
[[ -z "$API_KEY" ]] && die "API_KEY not set"
[[ "$env" == "prod" ]] && echo "⚠️  Production!"

# Regex
[[ "$email" =~ ^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$ ]]

# Pattern matching (glob)
[[ "$file" == *.tar.gz ]] && echo "Compressed archive"
[[ "$branch" == feature/* ]] && echo "Feature branch"

# Numeric
[[ $count -gt 0 ]] && echo "Has items"

# Combined
[[ -f "$file" && -r "$file" ]] && echo "Readable file"

case "$command" in
    start)
        start_service
        ;;
    stop)
        stop_service
        ;;
    restart|reload)          # multiple patterns
        stop_service
        start_service
        ;;
    *)                       # default (catch-all)
        echo "Usage: $0 {start|stop|restart}" >&2
        exit 1
        ;;
esac

case "$filename" in
    *.tar.gz|*.tgz)  tar xzf "$filename" ;;
    *.zip)           unzip "$filename" ;;
    *.deb)           dpkg -i "$filename" ;;
    *)               echo "Unknown format" >&2 ;;
esac

# Over literal values
for color in red green blue; do
    echo "$color"
done

# Over glob results
for file in *.log; do
    [[ -f "$file" ]] || continue
    echo "Processing: $file"
done

# Over array elements
servers=("web-01" "web-02" "db-01")
for server in "${servers[@]}"; do
    ping -c 1 "$server" &>/dev/null && echo "$server: UP"
done

for ((i = 0; i < 10; i++)); do
    echo "Iteration $i"
done

# Counter-based
count=0
while [[ $count -lt 5 ]]; do
    echo "Count: $count"
    ((count++))
done

# Read file line by line (CORRECT way)
while IFS= read -r line; do
    echo "Line: $line"
done < input.txt

# Infinite loop with break
while true; do
    read -rp "Continue? (y/n): " answer
    [[ "$answer" == "n" ]] && break
done

until ping -c 1 server.example.com &>/dev/null; do
    echo "Waiting for server..."
    sleep 5
done
echo "Server is up!"

# break — exit loop entirely
for i in {1..100}; do
    [[ $i -gt 10 ]] && break
done

# continue — skip to next iteration
for file in *.log; do
    [[ -s "$file" ]] || continue    # skip empty files
    process "$file"
done

while IFS= read -r line; do
    echo "$line"
done < "$filename"

while IFS=',' read -r name age city; do
    echo "$name is $age, lives in $city"
done < data.csv

# WRONG — breaks on spaces, expands globs
for line in $(cat file.txt); do ...
# "hello world" becomes TWO iterations: "hello" and "world"

# AND — run second only if first succeeds
[[ -d "$dir" ]] && cd "$dir"

# OR — run second only if first fails
[[ -f "$config" ]] || die "Config missing"
cd "$dir" || exit 1

# Combined: try or die with message
mkdir -p "$output_dir" || { echo "Cannot create dir" >&2; exit 1; }