Block sites in /etc/hosts

block-site-add.sh

#!/usr/bin/bash
#
# Removes a block to /etc/hosts.
#
# USAGE:
#
#     $ block-site-add.sh EXAMPLE.COM
#     0.0.0.0 example.com
#     0.0.0.0 www.example.com
#

SITE="${1}";
SITE="${SITE,,}";
SITE="${SITE#www.}";

ADDR="0.0.0.0";
FILE="/etc/hosts";
REGEX="^#?($ADDR\s+(www\.)?$SITE)$";

if [[ ! "$SITE" =~ .*\..* || -z "$SITE" ]];
then
    echo "Inform a site, for example: example.com"
    exit 1;
fi;

if [[  "`grep -E --count "$REGEX" "$FILE"`" -eq 0  ]];
then
    sudo bash -c "echo '$ADDR $SITE' >> '$FILE'";
    sudo bash -c "echo '$ADDR www.$SITE' >> '$FILE'";
    grep -E "${REGEX}" "$FILE";
else
    echo "Already exists.";
    exit 1;
fi;

block-site-remove.sh

#!/usr/bin/bash
#
# Removes a block from /etc/hosts.
#
# USAGE:
#
#     $ block-site-remove.sh EXAMPLE.COM
#     0.0.0.0 example.com
#     0.0.0.0 www.example.com
#

SITE="${1}";
SITE="${SITE,,}";
SITE="${SITE#www.}";

ADDR="0.0.0.0";
FILE="/etc/hosts";
REGEX="^#?($ADDR\s+(www\.)?$SITE)$";

if [[ ! "$SITE" =~ .*\..* || -z "$SITE" ]];
then
    echo "Inform a site, for example: example.com"
    exit 1;
fi;

if [[  "`grep -E --count "$REGEX" "$FILE"`" -eq 0  ]];
then
    echo "Not found.";
    exit 1;
else
    grep -E "$REGEX" "$FILE";
    sudo sed -E -i "/$REGEX/d" "$FILE";
fi;

block-site.sh

#!/usr/bin/bash
#
# Toggles a block entry in /etc/hosts, i.e. inserts or removes the pound symbol for a block entry.
#
# You can inform EXAMPLE or EXAMPLE.COM as parameter.
#
# List all block entries if no parameter is given.
#
# USAGE:
#
#     $ block-site.sh EXAMPLE (unblock)
#     #0.0.0.0 example.com
#     #0.0.0.0 www.example.com
#     $
#     $ block-site.sh EXAMPLE (block again)
#     0.0.0.0 example.com
#     0.0.0.0 www.example.com
#
#     $ block-site.sh ALL (unblock all sites in the list)
#     $ block-site.sh ALL (block all sites in the list again)
#

SITE="$1";
SITE="${SITE,,}";

FILE="/etc/hosts";
ADDR="0\.0\.0\.0";
REGEX="($ADDR\s+.*$SITE.*)";

if [[ -z "$SITE" ]]; then
    echo "List of sites:"
    grep -E "$REGEX" "$FILE" | sed -E "s/^(#?$ADDR)/\1/" | sed -E 's/\s+/ /g' | sed -E 's/^0/ 0/' | sed -E 's/www/zzz/' | sort | sed -E 's/zzz/www/';
    exit 0;
fi;

if [[ "$SITE" == "all" ]]; then
    REGEX="${REGEX/$SITE/}"
fi;

if [[ "`grep -E --count "^#$REGEX$" "$FILE"`" -gt 0 ]]; then
    sudo sed -E -i "s/^#$REGEX$/\1/" "$FILE"
else
    sudo sed -E -i "s/^$REGEX$/#\1/" "$FILE"
fi;

grep -E "^#?$REGEX" "$FILE" | sed -E 's/www/zzz/' | sort | sed -E 's/zzz/www/' || (echo "Not found."; exit 1);

Usage

Show the full block list:

$ block-site.sh
 0.0.0.0 facebook.com
 0.0.0.0 www.facebook.com

Unblock FACEBOOK:

$ block-site.sh FACEBOOK
#0.0.0.0 facebook.com
#0.0.0.0 www.facebook.com

Block FACEBOOK again:

$ block-site.sh FACEBOOK
0.0.0.0 facebook.com
0.0.0.0 www.facebook.com

Add AMAZON.COM to the block list:

$ block-site-add.sh AMAZON.COM
0.0.0.0 amazon.com
0.0.0.0 www.amazon.com

Show the full block list:

$ block-site.sh
 0.0.0.0 amazon.com
 0.0.0.0 facebook.com
 0.0.0.0 www.amazon.com
 0.0.0.0 www.facebook.com

Remove FACEBOOK.COM from the block list:

$ block-site-remove.sh FACEBOOK.COM
0.0.0.0 facebook.com
0.0.0.0 www.facebook.com

Show the full block list:

$ block-site.sh
 0.0.0.0 amazon.com
 0.0.0.0 www.amazon.com