Sometimes we are on connections that have a dynamic ip. This will add your current external ip to
Each time the script is run, it will
dig an OpenDNS resolver to grab your external ip. If it is different from what is in
~/.external-ip it will echo the new ip. Otherwise it will return nothing.
#!/bin/sh # Check external IP for change # Ideal for use in a cron job # # Usage: sh check-ext-ip.sh # # Returns: Nothing if the IP is same, or the new IP address # First run always returns current address # # Requires dig: # Debian/Ubuntu: apt install dnsutils # Solus: eopkg install bind-utils # CentOS/Fedora: yum install bind-utils # # by Sina Mashek <firstname.lastname@example.org> # Released under CC0 or Public Domain, whichever is supported # Where we will store the external IP EXT_IP="$HOME/.external-ip" # Check if dig is installed if [ "$(command -v dig)" = "" ]; then echo "This script requires 'dig' to run" # Load distribution release information . /etc/os-release # Check for supported release; set proper package manager and package name if [ "$ID" = "debian" ] || [ "$ID" = "ubuntu" ]; then MGR="apt" PKG="dnsutils" elif [ "$ID" = "fedora" ] || [ "$ID" = "centos" ]; then MGR="yum" PKG="bind-utils" elif [ "$ID" = "solus" ]; then MGR="eopkg" PKG="bind-utils" else echo "Please consult your package manager for the correct package" exit 1 fi # Will run if one of the above supported distributions was found echo "Installing $PKG ..." sudo "$MGR" install "$PKG" fi # We check our external IP directly from a DNS request GET_IP="$(dig +short myip.opendns.com @resolver1.opendns.com)" # Check if ~/.external-ip exists if [ -f "$EXT_IP" ]; then # If the external ip is the same as the current ip if [ "$(cat "$EXT_IP")" = "$GET_IP" ]; then exit 0 fi # If it doesn't exist or is not the same, grab and save the current IP else echo "$GET_IP" > "$EXT_IP" fi