Bash Script to Manage /etc/hosts file for adding/removing hostnames.

manage-etc-hosts.sh

#!/bin/sh

# PATH TO YOUR HOSTS FILE
ETC_HOSTS=/etc/hosts

# DEFAULT IP FOR HOSTNAME
IP="127.0.0.1"

# Hostname to add/remove.
HOSTNAME=$1

function removehost() {
    if [ -n "$(grep $HOSTNAME /etc/hosts)" ]
    then
        echo "$HOSTNAME Found in your $ETC_HOSTS, Removing now...";
        sudo sed -i".bak" "/$HOSTNAME/d" $ETC_HOSTS
    else
        echo "$HOSTNAME was not found in your $ETC_HOSTS";
    fi
}

function addhost() {
    HOSTNAME=$1
    HOSTS_LINE="$IP\t$HOSTNAME"
    if [ -n "$(grep $HOSTNAME /etc/hosts)" ]
        then
            echo "$HOSTNAME already exists : $(grep $HOSTNAME $ETC_HOSTS)"
        else
            echo "Adding $HOSTNAME to your $ETC_HOSTS";
            sudo -- sh -c -e "echo '$HOSTS_LINE' >> /etc/hosts";

            if [ -n "$(grep $HOSTNAME /etc/hosts)" ]
                then
                    echo "$HOSTNAME was added succesfully \n $(grep $HOSTNAME /etc/hosts)";
                else
                    echo "Failed to Add $HOSTNAME, Try again!";
            fi
    fi
}

@kucerarichard in your script I needed to change the msg function from 'exit 0' to 'return' so that it wouldn't exit unless run with verbose flag.

function msg() {
MESSAGE=$1
if [[ -z "${ALTER_VERBOSE}" ]]; then
exit 0
else
echo $MESSAGE
fi
}

To:

function msg() {
   MESSAGE=$1
   if [[ -z "${ALTER_VERBOSE}" ]]; then
      return
   else
      echo $MESSAGE
   fi
 }

What would be the downside/danger of looking at grep's exit code instead of comparing strings?

if grep -q $HOSTNAME /etc/hosts; then 
  # Entry already exists
else
   # Add in the entry
fi