UNIX for Dummies Questions & Answers

I want the date to be displayed in two digits.

I have written a script to calculate yesterday's date. I'm getting the yesterday's date as 2009085.

Desired output:

20090805


Find the script below:

#!/bin/ksh
### Script to get Yesterday Date #############
Y=`date +'%Y'`
M=`date +'%m'`
D=`date +'%d'`
today=$Y$M$D
echo $today
if [ $M -eq 01 -o $M -eq 03 -o $M -eq 05 -o $M -eq 07 -o $M -eq 08 -o $M -eq 10 -o $M -eq 12 ] && [ $D -eq 01 ];then
yesterday=$Y$M`expr $D + 30`
echo $yesterday
else
if [ $M -eq 04 -o $M -eq 06 -o $M -eq 09 -o $M -eq 11 ] && [ $D -eq 01 ]; then
yesterday=$Y$M`expr $D + 29`
echo $yesterday
else
if [ $M -eq 02 -a $D -eq 01 ]; then
yesterday=$Y$M`expr $D + 27`
echo $yesterday
else
yesterday=$Y$M`expr $D - 1`
echo $yesterday
fi
fi
fi


Thanks

Hi.

Perhaps you could try:

Code:

yesterday=$Y$M$(printf "%02d" $(expr $D - 1))

Or if you are in GMT timezone:

Code:

#!/bin/ksh
echo "Yesterday : $(TZ=GMT24BST;date +'%Y%m%d')"
echo "Today     : $(date '+%Y%m%d')"
echo "Tomorrow  : $(TZ=GMT-24BST;date '+%Y%m%d')"

Yesterday : 20090805
Today     : 20090806
Tomorrow  : 20090807

If the version of Korn Shell that you are using is ksh93, there is a much simplier way of doing it

Code:

$ printf "%(%Y%m%d)T\n" now
20090806
$ printf "%(%Y%m%d)T\n" yesterday
20090805

Does anyone actually use ksh93? It has some nice features, but it's never the default, never standard, and Solaris doesn't even ship with it (certainly none of the Solaris servers I look after has it) - which doesn't bode well for portability if you use it.

I'd be interested to know if it has a place.

Rarely used in portable shell scripts.

Actually it is the default shell on the latest version of OpenSolaris and Solaris. And Solaris has shipped with it for years. Just man dtksh. CDE relies on it.

And the Posix shell standard was mostly based on ksh93.

And if you want floating point support within a shell ....