Substracting days from current date(K shell script)

Shell Programming and Scripting
1

Hi,

I want to subtract 'n' days from the current timestamp in a k shell script. Is there any inbuilt function to do it
or any workaround solution to get the date. And I want the output to be in YYYY:MM:DD HH:MM:SS format. Please help.

Thanks in advance.

2

In ksh88, no there are no builtins to do what you want. You have to resort to perl or a ksh script that turns dates into JD, subtract days, then turn the new JD back into a date.

See cfa johnson's scripts for Julian dates:
8: The Dating Game

3

If you are using ksh93 you can use %T. For example to print the date 5 days ago:

$ printf "%(%Y:%m:%d %H:%M:%S)T\n" "5 days ago"
2011:02:05 10:20:15
$
4

May i know, how to get 10 days date from currentdate.

Like current date: 04-11-2011
I need: 03-28-2011.

I am using this but when i use it in my query the result is diffrent

Code: date -d "14 days ago"

5

Use this script with Number of days as the parameter

datefunction.ksh

 #!/bin/bash

sec2date (){
    date --utc --date "1970-01-01 $1 sec" "+%Y-%m-%d %T"
}

sec=86400
NDAYS=$1
SEC_DIFF=`expr $sec \* $NDAYS`

CURR_TS=`date "+%Y-%m-%d %T"`

dte1=`date --utc --date "$CURR_TS" +%s`
dte2=$((dte1-SEC_DIFF))

dte2op=$(sec2date $dte2)

echo "Current Timestamp:            $CURR_TS"
echo "Timestamp $1 days before:  $dte2op"
exit 0

Use like "datefunction.ksh 5"
Here 5 is the number of days