#!/bin/bash

# BASH doesn't actually understand booleans.
# What you can do however is to trick it by using the fact that the true and false commands return 0 and 1,
# so it can stand in for boolean algebra if used correctly.

BOOLEAN1=false

if $BOOLEAN1; then
    echo "We won't get here because BOOLEAN1 is false."
fi
if ! $BOOLEAN1; then
    echo "But we DO get here."
fi

BOOLEAN1=true

if $BOOLEAN1; then
    echo "Now we do get in this as it's been set to true."
fi
if ! $BOOLEAN1; then
    echo "And now we DON'T get here."
fi