get_month_name() 
{
case $1 in
01) month_name="Jan"
02) month_name="Feb"
03) month_name="Mar"
04) month_name="Apr"
05) month_name="May"
06) month_name="Jun"
07) month_name="Jul"
08) month_name="Aug"
09) month_name="Sep"
10) month_name="Oct"
11) month_name="Nov"
12) month_name="Dec"
}

month=`date +%m`
year=`date +%Y`

month=$(( ${month} - 1 ))

if [[ ${month} -eq 0 ]]; then
month=12
year=$(( ${year} - 1 ))
fi
if [[ ${month} -lt 10 ]]; then # prefix a zero in front of
month=0${month}
fi
get_month_name "${month}"

echo ${month_name}${year}