#!/bin/sh

log_file="/tmp/ping.log"

do_ping() {
  (
    echo "==== Starting ping at `date` ===="
    echo
    ping 4.2.2.2 -c 4
    echo
    echo "==== Ping done at `date` ===="
    echo
  ) 2>&1 >> "$log_file"
}

(sleep 30; do_ping) &
do_ping