#!/bin/sh
[ "$1" ] || { cat <<EOS
  execute the specified command at the top of each hour
  or \$minute after the top of each hour

  Note that setting minute to 60 will run the command
  every other hour, 120 implies every third, etc.

  the \$hrMins environment variable determines number of minutes
  in a logical hour.

  examples:
    hourly date  #show at the top of every hour
    minute=15 start hourly upload  #upload 15 minutes after top of each hour
    hrMins=15 start hourly upload  #upload every quarter hour
EOS
exit
}

[ -z "$minute" ] && minute=0
[ -z "$hrMins" ] && hrMins=60

while :; do
  now=`date +%M` || exit 2
  sleep `expr \( \( 59 - $now \) % $hrMins + $minute + 1 \) \* 60` || exit 3
  $@
done