how can i get yesterday in yyyymmdd format?

with gnu date you can do:

date --date="-1 days" +%Y%m%d

if you have issue with the above method say you dont have gnu date... try connecting to oracle and get date from there...as there is no direct mechanism to calculate date.

something like this ...

yesterday=`sqlplus user/password << EOF
Select to_char(sysdate-1,'YYYYMMDD') from dual
Exit
EOF`

I wrote this script to convert julian date into dd-mm-yyyy format. You could use this to get yesterday's date. You just have to get today's julian date (get this using `date +%j`) and subtract 1 from it. This will get you yesterday's julian date. Give this as the second argument to the script. The first argument is the present year in the YYYY format.

Note: I have changed the output so that it prints YYYYmmdd.

[edit]
Also this script will blindly convert whatever the julian date that is given to it. No error checking is done - so if you give the julian date as 0, the output you get for this year is 20050100
[/edit]

#!/bin/sh

check_done() {
        if [ $month -eq 1 -o $month -eq 3 -o $month -eq 5 -o $month -eq 7 -o $mo
nth -eq 8 -o $month -eq 10 -o $month -eq 12 ]
        then
                daysofmth=31
        elif [ $month -eq 2 ]
        then
                if [ `expr $year % 100` -eq 0 -a `expr $year % 400` -eq 0 ]
                then
                        daysofmth=29
                elif [ `expr $year % 100` -ne 0 -a `expr $year % 4` -eq 0 ]
                then
                        daysofmth=29
                else
                        daysofmth=28
                fi
        elif [ $month -eq 4 -o $month -eq 6 -o $month -eq 9 -o $month -eq 11 ]
        then
                daysofmth=30
        fi
        julday=`expr $julday - $daysofmth`
        if [ $julday -lt 0 ]
        then
                done=1
                julday=`expr $daysofmth + $julday`
        elif [ $julday -eq 0 ]
        then
                done=1
                julday=$daysofmth
        fi
}
#########  main script starts here
if [ $# -ne 2 ]
then
        echo "Usage: fromjul <yyyy> <julian day>"
        exit 1
fi

year=$1
julday=$2

month=0
done=0

while [ $done -ne 1 ]
do
        month=`expr $month + 1`
        check_done
done

printf "%.4d%.2d%.2d\n" $year $month $julday

This does works exept for the 1st day of the month.

date | awk '{printf"%4d%2d%2d\n",$6,$2,($3-1)}' | sed 's/ /0/g'

date | awk '{printf"%4d%2d%2d\n",$6,$2,($3-1)}' | sed 's/ /0/g'

My env is Japanese, so this happened.
Thank you for modification!