roms_bookend

#! /usr/bin/env bash

# Script to add "bookend" records at the beginning and end of
# a ROMS file. This is to be used for (say) the case where we
# have daily-average climatology or forcing data for one year
# and we need data to drive a simulation during the first and
# last 0.5 days of the year.

# Currently there must be an unlimited dimension representing time
# with units of days.

set -e

# Check arguments. If a second file name is not provided, overwrite
# the existing file.

if test -n "$1"
then
    i=$1
else
    echo "Input file name not specified" 1>&2
    exit 1
fi

if !(test -f ${i})
then
    echo "Input file "${i}" does not exist" 1>&2
    exit 1
fi

if test -n "$2"
then
    o=$2
else
    o=${i}
fi

# Use ncdump to establish the name of the unlimited dimension & the
# number of records. For info on shell brace expansions, see
# http://www.ibm.com/developerworks/library/l-bash.html#N1010B

d=$(ncdump -h ${i} | grep "UNLIMITED ; //" | cut -d " " -f 1)
d=${d:1}

n=$(ncdump -h ${i} | grep "UNLIMITED ; //" | cut -d " " -f 6)
n=${n#*(}

# Save the first & last records into separate files and modify their times by
# -50 and +50 days respectively.

ncks -O -d ${d},0 ${i} ${i}.tmp0
ncap -O -s "${d}=${d}-50.0" ${i}.tmp0 ${i}.tmp0
ncatted -O -a units,${d},c,c,days ${i}.tmp0 ${i}.tmp0

ncks -O -d ${d},$((n-1)) ${i} ${i}.tmp1
ncap -O -s "${d}=${d}+50.0" ${i}.tmp1 ${i}.tmp1
ncatted -O -a units,${d},c,c,days ${i}.tmp1 ${i}.tmp1

ncrcat -O -o ${o} ${i}.tmp0 ${i} ${i}.tmp1

rm ${i}.tmp0 ${i}.tmp1