Nested Controls: Combining Control Structures

Nested controls combine if, loops, case. Complex logic.

Here's the thing: Nested controls are powerful. But keep them simple. Don't nest too deep.

Nested If

if [ "$status" = "active" ]; then
    if [ "$count" -gt 10 ]; then
        echo "Active and many"
    else
        echo "Active but few"
    fi
else
    echo "Inactive"
fi

My take: Nested if works. But keep it simple.

Loop With If

for file in *.txt; do
    if [ -f "$file" ]; then
        process "$file"
    fi
done

My take: Loops with if are common. Use them.

Complex Nesting

for dir in */; do
    if [ -d "$dir" ]; then
        case "$dir" in
            "important"*)
                for file in "$dir"/*; do
                    if [ -f "$file" ]; then
                        process "$file"
                    fi
                done
                ;;
        esac
    fi
done

My take: Complex nesting works. But keep it readable.

Common Patterns

Nested Loops

for i in {1..3}; do
    for j in {1..3}; do
        echo "$i $j"
    done
done

Common Mistakes (I've Made These)

1. Too deep nesting: Keep nesting shallow. 2-3 levels max.

2. Hard to read: Complex nesting is hard to read. Simplify.

3. Not using functions: Functions reduce nesting. Use them.

What's Next?

Now that you understand nested controls, you can write complex logic. Or review Control Flow to reinforce.

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Personal note: I used to nest deeply. Then code was hard to read. Now I keep it shallow. Use functions. It's better.