Shell Programming and Scripting

TODAY=`date +%w`
BASESLOT=4096
SLOT=$(($BASESLOT + $TODAY))

inventory()
{
  echo "Tape Inventory"
  echo " "

  query_inventory
  query_drive

  echo "Slot  - Tape"
  i=0
  while [ $i -lt $MAXSLOTS ]
  do
    echo "$(($BASESLOT + $i))  - ${SLOTS[$i]}"
    ((i=$i+1))
  done

  echo " "
  echo "Drive - $TAPEINDRIVE"
  echo " "
}

load()
{
  query_inventory
  query_drive

  TAPEINSLOT=${SLOTS[$TODAY]}

  if [[ $TAPEINSLOT = " " ]]; then
    echo "Unable to load tape - today's slot is empty"
    exit
  fi

  if [[ $TAPEINDRIVE != "None" ]]; then
    echo "Unable to load tape - tape $TAPEINDRIVE is already in the drive"
    exit
  fi

  echo "Moving tape $TAPEINSLOT from slot $SLOT to drive"

  RETURN=`$ITDT -f $DEVICE move $SLOT $DRIVE`
  
}

query_drive()
{
  TAPEINDRIVE=`$ITDT -f $DEVICE inventory | \
    grep -p "Drive Address" | grep 'Volume Tag' | cut -c 34-42`

  [[ $TAPEINDRIVE = " " ]] && TAPEINDRIVE="None"
}

query_inventory()
{
  INVENTORY=$($ITDT -f $DEVICE inventory)

  i=0
  while [ $i -lt $MAXSLOTS ]
  do
    TMPSLOT=$(($BASESLOT+$i))
    SLOTS[$i]=`echo "$INVENTORY" | \
      grep -p "Slot Address ................... $TMPSLOT" | \
      grep 'Volume Tag' | cut -c 34-42`
    ((i=$i+1))
  done
}

unload()
{
  query_inventory
  query_drive

  if [[ $TAPEINDRIVE = "None" ]]; then
    echo "Drive is empty. There is nothing to unload!"
    exit
  fi

  if [[ ${SLOTS[$TODAY]} != " " ]]; then
    echo "Todays slot is occupied. Looking for available slot"
    SLOT="Occupied"
    i=0
    while [ $i -lt $MAXSLOTS ]
    do
      if [[ ${SLOTS[$i]} = " " ]]; then
        SLOT=$(($BASESLOT + $i))
        echo "Found available slot $SLOT"
        break
      fi
      ((i=$i+1))
    done
    if [[ $SLOT = "Occupied" ]]; then
      echo "Unable to find a free slot. Unable to unload tape"
      exit
    fi
  fi

  echo "Moving tape $TAPEINDRIVE from drive to slot $SLOT"

  RETURN=`$ITDT -f $DEVICE move $DRIVE $SLOT`


}

usage()
{
  echo "   usage: tapes load"
  echo "          tapes unload"
  echo "          tapes inventory"
  echo " "
}

if [ $# != 1 ]; then
  usage
  exit
fi

DEVICE=/dev/rmt0
ITDT=/usr/local/bin/itdt
DRIVE=256
TODAY=`date +%w`
BASESLOT=4096
SLOT=$(($BASESLOT + $TODAY))
MAXSLOTS=23
TAPEINDRIVE="None"

case "$1" in
  load) load; exit;;
  unload) unload; exit;;
  inventory) inventory; exit;;
  *) usage; exit;;
esac

DATE=$(date '+%j')	# Get Julian day of year.
DATE=${DATE#0}		# Strip leading zeros to guarantee decimal (rather
DATE=${DATE#0}		# than octal) evaluation of DATE when computing SLOT.
BASESLOT=4096
SLOT=$((BASESLOT + 1 + ((DATE - 1) % 23)))

SLOT=$((BASESLOT + 1 + ((DATE - 1) % 23)))

SLOT=$((BASESLOT + ((DATE - 1) % 23)))