Section 11.1: 无限循环

while true; do
        echo ok
done

or

while :; do
        echo ok
done

or

until false; do
        echo ok
done

Section 11.2: 函数返回

function positive() {
        return 0
}

function negative() {
        return 1
}

Section 11.3: 永远/从不执行的代码

if true; then
        echo Always executed
fi
if false; then
        echo Never executed
fi