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#!/bin/sh

ROOT_DIR=/path/to/data
START_DATE='19950101'
END_DATE='20161231'

cd $ROOT_DIR

# Loop over all dates within the given date range
curr_date=$START_DATE
until [[ $curr_date == $(date --date "$END_DATE 1 day" +%Y%m%d) ]] ; do
    yyyy=${curr_date:0:4} ; mm=${curr_date:4:2} ; dd=${curr_date:6:2}
    dir="$yyyy/$mm/$dd/00"
    if [[ -d $dir ]] ; then
        # Loop over all files in $dir
        (
        cd $dir
        find . -name '*.grb' -print0 | while IFS= read -r -d $'\0' file ; do
            # Get the fhr
            fhr=$(echo $file | perl -ne '/_f(\d+)_/ && printf("%.0f", $1)')
            # Remove grib records that don't have the correct fhr
            if [[ "$fhr" == '0' ]] ; then
                fhr_str=":anl:"
            else
                fhr_str=":${fhr}hr fcst:"
            fi
            cmd="wgrib $file | grep '$fhr_str' | wgrib -i $file -grib -o temp.grb  >& /dev/null && mv -f temp.grb $file"
            # echo $cmd
            eval $cmd
        done
        )
    fi
    curr_date=$(date --date "$curr_date 1 day" +%Y%m%d)
done