Re: date minus one

On Tue, 29 Mar 2005 12:55:06 -0600, Knight, Jon <jknight_at_concordefs.com> wrote:
> Just curious how the rest of the world gets "yesterday" in UNIX. We're
> running Solaris and we execute a sqlplus script with "select sysdate-1 from
> dual;" and pipe it to tail to set an environment variable.
>
> Is there a more UNIXy way, -or- maybe a java function. Any suggestions
> welcome.
>
> TIA,
> Jon Knight

I've done it in a shell script before, I don't remember exactly the commands but I do recall it was a lot more complex than it looks at first.

As I recall it's something like:

• Get current date
• Check day value.
• If day is later than first then decrement by 1 and return along with existing month and year value.
• If day is 1 and month is not 1 (i.e. it's first of any month but January) then decrement month by one and find last day of new month and put into day value. If month is 2 (i.e. February) check if is a leap year (year divisible by 4 but not by 400) and select 28 or 29 for day value.
• If day is 1 and month is 1 then decrement year and set day to 31 and month to 12.

It's a lot of nested case statements.

Stephen

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