Date von gerstern

#!/bin/bash

d=`date +%d`
m=`date +%m`
y=`date +%Y`

#Yesterday-Funktion

getYesterday()
{
        day=$1
        month=$2
        year=$3
        if [ $day -eq 01 ]
        then
                if [ $month -eq 01 ]
                then
                        month=12
                        year=`expr $year - 1`
                else
                        month=`expr $month - 1`
                fi

                day=`cal $month $year | awk 'NF != 0{ last = $0 }; END{ print last }' |  awk '{ print $NF }'
`
        else
                day=`expr $day - 1`
        fi
        echo  $day $month $year
}