blockit.bash

#!/usr/bin/env bash
# Block any number of sites in your web browser for any length of time

# Takes a list of sites from a text file called sites
# and blocks access to them for a certain number of 
# minutes. Note: One site url per line, no http://, no www,
# (www gets added programmatically), like so:
# facebook.com
# twitter.com
# reddit.com
# (without the #-space, of course)
#
# Use --add / -a followed by the number of minutes
# to add a block. 
#
# Example:
# sudo ./blockit.bash -a 180
#
# Use --check / -c to check if the sites should still be blocked.
# This would ordinarily be done on the crontab.
#
# Currently this script must be run via sudo.

# What arguments do we pass?
while [ "$1" != "" ]; do
    case $1 in
        -a | --add )            shift
				minutes=$1
                                ;;
        -c | --check )		check=1
                                ;;
        -t | --time )		TIME=1
                                ;;
    esac
    shift
done

NOW=`date +%s`

if [[ "$TIME" == 1 ]]; then
	# See how much time we've got left.
	THEN=`cat control`
	DIFF=$(($THEN-$NOW))
	echo "`echo $(($DIFF/60))` minutes left"
fi

if [[ "$check" == 1 ]]; then
	# Compare the current time against the control time.
	THEN=`cat control`

	# In case we've got crontab edits
	crontab -l | sed '/###START-blockit/,/###END-blockit/d' > cron
	test "$NOW" -ge "$THEN" && ( sed -i '/###START-blockit/,/###END-blockit/d' /etc/hosts; > control; crontab cron; echo "Unblocking sites"; )
	rm cron
fi

if [[ "$minutes" > 0 ]]; then
	# Make sure we're not overwriting an existing block
	test `cat control | wc -m` -ge 0 && ( echo 'No overwrites!'; exit 2 )

	# Remove any existing blocks, instructions.
	sed -i '/###START-blockit/,/###END-blockit/d' /etc/hosts
	> control

	# Keep track of when we should remove these lines from the hosts file.
	SECONDS=$(($minutes*60))
	THEN=$(($NOW+$SECONDS))
	echo $THEN > control

	# Edit the hosts file
	echo '###START-blockit' >> /etc/hosts
	for i in $(cat sites); do 
		echo "127.0.0.1 $i" >> /etc/hosts;
		# If there's no www in the url, we add the www version just to be safe.
		if [[ $i != 'www*' ]]
		then
			echo "127.0.0.1 www.$i" >> /etc/hosts;
		fi
	done
	echo '###END-blockit' >> /etc/hosts
	echo "These sites will be unblocked after $minutes minutes."

	# Update the crontab
	(crontab -l; echo '###START-blockit'; echo "* * * * * cd `pwd`/; sudo ./blockit.bash -c"; echo '###END-blockit') | crontab -

fi