Shell Programming and Scripting

i have a paramter data_date in which i am passing a string value.i want to find out another paramter file_date from this.the logic is given below

if day of data_date = sunday or monday
then
file_date=data_date-1
else
file_date=data_date-2

i am passing data_date as 20061027.
how can i write a script that can meet the above requirement.

If your version on unix supports it, this might work for you. I'm unsure of what you are wanting to do with the data_date-1.. are you trying to go one day back? So if it's Sunday it would be Saturday and Monday it would be Sunday??:

Code:

data_date_day=`date -d "$data_date" | cut -d " " -f 1`
if [ $data_date_day = "Sun" -o $data_date_day = "Mon" ];then
   file_date=whatever
else
   file_date=whatever
fi

Dupe Post.

my requirement is say data_date=20071028 is sunday and data_date=20071029 is monday then for this two days
file_date will be 20071026 and 200727.and rest otherdays file_date is data_date-1.if data_date=20071030 is tuesday then file_date is 20071029.and similar till saturday.
please tell me the whole script.
i want to pickup a file based on file_date from data_date.
please sugegst a script.