#!/bin/sh
prog=`basename $0`
[ "$2" ] || { cat >&2 <<EOS
  bring up the ppp link every \$1 minutes for \$2 minutes
  default link is drifter but this may be specified as via \$iface env variable 
  
  examples:
    $prog 20 5  #bring up the drifter ppp link for 5 minutes every 20 min
    $prog 30 10 update  #bring up link for 10 min every 30 min.
                               #run update every time link comes up
EOS
exit 1
}

interval=$1
upTime=$2
shift 2
: ${iface:=drifter}
[ "$upTime" -ge "$interval" ] && {
  echo "Cycle interval must be longer than scheduled link up time" >&2
  exit 2
}
downTime=`expr $interval - $upTime`
echo "call $iface every $interval minutes for $upTime minutes"
[ "$*" ] && echo "run \"$@\" at the start of each call"
hangup $iface
while :; do
  while :; do
    call $iface
    retCode=$?
    [ $retCode = 0 ] && break
    [ $retCode -ge 128 ] && exit $retCode
    echo "`date` -- call $iface failed, retrying after 20 seconds..."
    sleep 20
  done
  echo "`date` -- $iface link is up for the next $upTime minutes"
  "$@" &
  sleep ${upTime}m
  hangup $iface
  echo "`date` -- $iface link will remain down for the next $downTime minutes"
  sleep ${downTime}m
done