[W]ait [U]ntil [P]ort [I]s [A]ctually [O]pen

wupiao

#!/bin/bash
# usage: wupiao [ip] [port]
#   inspired by script of same name from Kubernetes project
#   we're going to test any port, though, not just HTTP
[ -n "$1" ] && [ -n "$2" ] && while ! nc -z $1 $2; do sleep 1 && echo -n .; done;
exit $?