#!/bin/ksh

# Get the NCEP ice ancillary data file closest to a MODIS granule date and time

# Check number of arguments
if [ $# != 3 ]; then
  echo "Usage: get_icec dir date time"
  echo "  dir  is the directory containing the NCEP ice files"
  echo "  date is the date (yyyyddd)"
  echo "  time is the time (hhmm)"
  exit 1
fi

# Get arguments
dir=$1
date=$2
time=$3

# Find the closest date within a 28 day window
for delta in 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14; do

  list="- +"
  for sign in $list; do
  
    # Compute the Gregorian date (yyyymmdd) of the closest NCEP ice file
    modis_date=`dateplus -J $date`
    ice_date=`dateplus $sign$delta $modis_date | cut -c3-8`

    # Find the NCEP ice file
    ice_name="eng."$ice_date
    ice_file=`find $dir -size +226000c -name $ice_name`
 
    # Check for success
    if [[ $ice_file != "" ]]; then
      echo $ice_file
      exit 0
    fi
    
  done
  
done

# If we get here, no matching NCEP ice file was found
exit 1