Website-Blocking Timer on MacOS

focus_timer.sh

# Programming Life Hacks #1: Website-Blocking Focus Timer
# Copyright (c) 2020 Dickson Tsai
# Follow along on my Youtube: https://youtu.be/kCo9DAuLGX4

# Disclaimer: This file is primarily for teaching purposes.
# 1. USE THIS SOLUTION AT YOUR OWN RISK. sudo is always risky to use.
# 2. Not the most idiomatic bash/zsh, but it works for me.

# General procedure
# 1. Setup website blocking
#    - We will edit /etc/hosts to route websites back to our computer.
#    - Provide your copy in ./unprod_hosts.
# 2. Count 30 minutes
# 3. Tear down website blocking
# 4. Notify the user

# Key insight:
# /etc/hosts is a file. You can manipulate it as with any other file (cp, mv, etc.).

# Make sure this file does not exist. Use `ls -a` to view hidden files (files
# that start with ".", like ".real_hosts").
REAL_HOSTS_TEMP=./.real_hosts

# Make sure you have a file unprod_hosts in the same directory as this script.
UNPROD_HOSTS=./unprod_hosts

# Use a variable for /etc/hosts so all code references use the same definition.
ETC_HOSTS=/etc/hosts

echo "Setting up focus timer"
if [ -f $REAL_HOSTS_TEMP ]; then
    echo "Focus timer already active???"
    exit 1
fi
if [ ! -f $UNPROD_HOSTS ]; then
    echo "Please provide an $UNPROD_HOSTS file"
    exit 1
fi

echo "Replacing $ETC_HOSTS file with $UNPROD_HOSTS"
# sudo not needed for reading /etc/hosts.
# root has read and write permissions. user (you) only have read permissions.
# -rw-r--r--  1 root  wheel   659B ... /etc/hosts
cp $ETC_HOSTS $REAL_HOSTS_TEMP
# sudo is needed for writing to /etc/hosts from your account.
sudo cp $UNPROD_HOSTS $ETC_HOSTS

# What happens if my new /etc/hosts doesn't do anything?
# 1. Try restarting your browser.
# 2. Not recommended: Try clearing your DNS cache:
#        sudo dscacheutil -flushcache

echo "Starting focus timer"
for i in {30..1}
do
    echo "$i minutes remaining"
    sleep 60
done

echo "Reverting $ETC_HOSTS file back to the original"

# Send notification to MacOS
# You may need to type in your password again. Add that to the message body.
osascript -e 'display notification "Congratulations! Your focus timer is up. Visit the terminal to check your hosts file." with title "Focus Timer Complete" sound name "Glass"'

sudo cp $REAL_HOSTS_TEMP $ETC_HOSTS
rm $REAL_HOSTS_TEMP

# Further ideas
# 1. Interrupt handling, to end the timer early but safely.
# 2. Command line flags for adjusting the duration.
# 3. Notifications to encourage you to keep focusing.