Wait for an interface to have an IP address

wait-for-interface

#!/bin/sh

INTERFACE=$1
if [ -z $INTERFACE ]; then
    echo "Usage: wait-for-interface [interface name]"
    exit 1
fi

echo "Wait for $INTERFACE to have an IP address..."

while ! ip addr show $INTERFACE | grep inet >/dev/null; do
    # Wait a small amount of time before checking again
    sleep 0.1
done