Bash script to get the private and public IP address per network interface

ips

#!/bin/bash

# A command-line tool to get the private and public ip address per network
# interface for Mac and Linux.
#
# Dependencies:
# - MacOS: ifconfig
# - Linux: ip
#
# Installation:
# Only move the directory to a bin directory depending on where you want to 
# have the script available.
# 
# In the gist page, copy the raw url, then:
#
# curl -L https://gist.githubusercontent.com/juanpagfe/{GIST_HASH}/raw/{GIST_VERSION/ips -o ~/.local/bin/ips
# chmod a+x ~/.local/bin/ips
# 
# Usage:
# The script can receive network interfaces as positional arguments or it will 
# get them by itself if you want a result for all NICs
# 
# Usage with a NIC:
# ips en0
#
# Usage without nic:
# ips

# Gets the operating system name
unameOut="$(uname -s)"
case "${unameOut}" in
    Linux*)     export OS=Linux;;
    Darwin*)    export OS=Mac;;
    CYGWIN*)    export OS=Cygwin;;
    MINGW*)     export OS=MinGw;;
    *)          export OS="UNKNOWN:${unameOut}"
esac

usage() {
    echo -e "Tool to get the local and public IP address per network interface. You can choose the NIC as well giving it as an argument\n"
    echo "Usage: $0 [options] <network-interface-name>"
    echo "Options:"
    echo "  -h, --help      Show this help message"
}

wargs=false

while [[ $# -gt 0 ]]; do
    case "$1" in
        -h|--help)
            usage
            exit 0
            ;;
        *)
            NICS=("$@")
            wargs=true
            shift
            break
            ;;
    esac
done

if [[ $# -eq 0 && -z "$NICS" ]]; then
    if [[ "$OS" = "Linux" ]]; then
        NICS=($(ip addr list | awk -F': ' '/^[0-9]/ {print $2}'))
    elif [[ "$OS" = "Mac" ]]; then
        NICS=($(ifconfig | pcregrep -M -o '^[^\t:]+(?=:([^\n]|\n\t)*status: active)'))
    else
        NICS=("$@")
    fi
fi

first=true
for nic in "${NICS[@]}"; do
    if [[ "$nic" != "lo" && "$nic" != "lo0" ]]; then
        if [[ "$OS" = "Linux" ]]; then
            ip=$(ip -4 addr show $nic | grep -oP "(?<=inet ).*(?=/)")
        elif [[ "$OS" = "Mac" ]]; then
            ip=$(ifconfig $nic | grep -E "([0-9]{1,3}\.){3}[0-9]{1,3}" | head -1 | awk '{ print $2 }')
        fi
        if [[ ! -z $ip ]]; then
            pubip=$(curl --interface $nic -s ipinfo.io/ip; echo)
            if [ "$first" = true ]; then
                first=false
                echo "------------------------------------"
            fi
            echo "$nic: $ip | $pubip" | awk -F '[:| ]+' '{print "Network Interface: " $1 "\nLocal IP: " $2 "\nPublic IP: " $3}'
            echo "------------------------------------"
        else
            if $wargs; then
                echo "The network interface '$nic' does not have a local ip address or does not exist."
                exit 1
            fi
        fi
    fi
done