libexec

sntp-wrapper

#!/bin/sh

# Cribbed from /usr/libexec/ntpd-wrapper. Will wait for DNS to be available before
# invoking sntp, but does not need to handle starting a server, or any configurability.
# Intended for use in the BaseSystem only.

PATH=/usr/sbin:/usr/bin:/bin
TIMEOUT=30
KEY=State:/Network/Global/DNS
DNS=/var/run/resolv.conf
# sentinel to special case DNS readiness at boot
LOG=/var/run/sntp.log

ipconfig waitall

if [[ ! -f ${LOG} ]]; then
    DEADLINE=$((SECONDS+TIMEOUT))
    for (( CURTIMEOUT=TIMEOUT; SECONDS < DEADLINE; CURTIMEOUT=DEADLINE-SECONDS )); do
	if scutil -w ${KEY} -t ${CURTIMEOUT}; then
	    if [[ -f ${DNS} ]]; then 
			break;
	    fi			# else retry false alarms
	else
	    logger -p daemon.err "$0: scutil key ${KEY} not present after ${TIMEOUT} seconds"
	    break;
	fi
    done
fi

sntp -s time.apple.com