manage /etc/hosts file

hosts_m.sh

#!/bin/bash
# manage /etc/hosts
isIp() {
    # test variable is an ip address or not
    # true: return 0
    # false: return 1
    local ip=$1
    local stat=1
    if [[ $ip =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$ ]]; then
        OIFS=$IFS
        IFS='.'
        ip=($ip)
        IFS=$OIFS
        [[ ${ip[0]} -le 255 && ${ip[1]} -le 255 \
            && ${ip[2]} -le 255 && ${ip[3]} -le 255 ]]
        stat=$?
    fi
    return $stat
}

if [[ -n "$1" ]] && [[ -n "$2" ]]; then
    a="$1"
    b="$2"
    if isIp "$a"; then
        ip="$a"
        name="$b"
    elif isIp "$b"; then
        ip="$b"
        name="$a"
    else
        exit 2
    fi
    if grep -wq "$name$" /etc/hosts; then
        sed -i "/ $name$/d" /etc/hosts
    fi
    echo "$ip $name" >> /etc/hosts
elif [[ -n "$1" ]]; then
    name="$1"
    sed -i "/ $name$/d" /etc/hosts
else
    exit 1
fi