Bash

Loop Control — break, continue, and Nested Loops

Control loop execution with break (exit early) and continue (skip to next iteration). Understand how they interact with nested loops and how to target specific loop levels.

January 15, 20265 min read

BashLoopsbreakcontinueScripting

Sometimes you need to exit a loop early when a condition is met (break), or skip the rest of the current iteration and jump to the next one (continue). Both work with for, while, and until loops.

break — Exit the Loop

# Find first matching file and stop
for file in *.log; do
    if grep -q "CRITICAL" "$file"; then
        echo "Found CRITICAL in: $file"
        break    # stop searching after first match
    fi
done

# Infinite loop with break condition
while true; do
    read -rp "Enter 'quit' to exit: " input
    if [[ "$input" == "quit" ]]; then
        echo "Goodbye!"
        break
    fi
    echo "You said: $input"
done

continue — Skip to Next Iteration

# Process only .sh files that start with "deploy"
for file in *.sh; do
    if [[ "$file" != deploy* ]]; then
        continue    # skip non-deploy scripts
    fi
    echo "Deploying: $file"
    bash "$file"
done

# Skip blank lines and comment lines when processing config
while IFS= read -r line; do
    [[ -z "$line" ]] && continue          # skip blank
    [[ "$line" == "#"* ]] && continue     # skip comments
    echo "Config: $line"
done < config.txt

Nested Loops — Targeting Levels

break and continue with a numeric argument target outer loop levels. break 2 breaks out of two loop levels at once.

# Nested loop — break/continue target the innermost by default
for i in 1 2 3; do
    for j in a b c; do
        if [[ "$j" == "b" ]]; then
            break       # breaks inner loop only
        fi
        echo "$i-$j"
    done
    echo "Back in outer loop: i=$i"
done
# 1-a (then break inner), 2-a (then break inner), 3-a (then break inner)

# break 2 — exits both loops
found=""
for server in web1 web2 db1; do
    for port in 80 443 8080; do
        if nc -z "$server" "$port" 2>/dev/null; then
            found="$server:$port"
            break 2    # exit both for loops immediately
        fi
    done
done
echo "First open: $found"

continue N

continue 2 skips to the next iteration of the outer loop. Like break N, it counts loop levels from the inside out.

select — Interactive Menu Loop

Bash's built-in select loop automatically builds a numbered menu and loops until you break:

PS3="Choose an option: "    # the prompt for select

select option in "List files" "Check disk" "Exit"; do
    case "$option" in
        "List files")
            ls -la
            ;;
        "Check disk")
            df -h
            ;;
        "Exit")
            echo "Bye!"
            break
            ;;
        *)
            echo "Invalid choice: $REPLY"
            ;;
    esac
done

Quick Check

In a three-level nested loop, what does `break 2` do?

Exercise

Write a script that:

Loops from 1 to 20
Skips even numbers (use continue)
Prints "found 13!" and stops when it reaches 13 (use break)
For all other odd numbers, prints the number