Yesterday's date in unix

priyophan · 03-29-2011, 12:24 AM

#!/usr/bin/perl
$presentdate=`date +"%m-%d-%Y"`;
@datearray=split('-',$presentdate);
$mm=$datearray[0];
$dd=$datearray[1];
$yy=$datearray[2];
if ( $dd > 2 )
{
$dd-=1;
}
elsif ( $mm == ( 5 || 7 || 8 || 10 || 12 ))
{
$dd = 30;
$mm = $mm-1;
}
elsif ( $mm == 1 )
{
$dd=31;
$mm=12;
$yy=$yy-1;
}
elsif ( $mm == 3 )
{
$rem=$yy%4;
$mm=$mm-1;
$dd=29 if $rem==0;
$dd=28 if $rem!=0;
}
elsif ( $mm == ( 2 || 4 || 6 || 9 || 11 ))
{
$dd=31;
$mm=$mm-1;
}
$date = ($mm . "-$dd" ."-$yy");
printf ("%s \n", $date);

evo2 · 03-29-2011, 01:32 AM

How about:

Code:

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

Evo2.

jlinkels · 03-29-2011, 01:43 AM

The OP asked about yesterday's date:

Code:

date -d "yesterday"  +"%Y-%m-%d"

lol

jlinkels

evo2 · 03-29-2011, 03:12 AM

Quote:

Originally Posted by jlinkels

The OP asked about yesterday's date:

Code:

date -d "yesterday"  +"%Y-%m-%d"

Wow. Seeing that rings a bell, I must a have read somewhere that date will take natural language. Seems that things like "last week" work too.

Cheers,

Evo2.

colucix · 03-29-2011, 03:40 AM

Actually the OP did not ask anything. The perl solution works and I guess the script is meant to be used on Unix machines where the date command lacks the -d, --date option. I used a C program in the good ol' days of IRIX or SUN SPARC for the same reason.

evo2 · 03-29-2011, 05:06 AM

Quote:

Originally Posted by colucix

Actually the OP did not ask anything. The perl solution works

The OPs solution does not treat leap years correctly.
See for example: http://en.wikipedia.org/wiki/Leap_year#Algorithm

Cheers,

Evo2.

priyophan · 03-30-2011, 12:57 AM

Thnx everyone for the response , I was looking for something that works universally on hpux ,solaris and linux ,the options provided above work on linux mainly and over a leap year I was not sure so I thought it would be better to use something universally valid .

archtoad6 · 03-31-2011, 12:09 PM

Quote:

Originally Posted by jlinkels

The OP asked about yesterday's date:

Code:

date -d "yesterday"  +"%Y-%m-%d"

lol

jlinkels

If you want some real fun:

Code:

for D in {yester,to,sun,mon,tues,wednes,thurs,fri,satur}day; 
do printf "%10s:  %s  %s  %s  %s\n" $D \
 `date -d "last $D" +"%F"` \
 `date -d "$D" +"%F"`      \
 `date -d "next $D" +"%F"` \
 `date -d "$D week" +"%F"`; 
done

jlinkels · 03-31-2011, 01:23 PM

Yeah, I know. Most people overlook the power of date. I have written fairly complicated Bash scripts using date and time and date is invariably your friend.

However, a few weeks ago someone asked to find the last Sunday in March and the last Sunday in October. That was something date could not do.

jlinkels

smallpond · 03-31-2011, 03:07 PM

A better Perl function is:

#!/usr/bin/perl
use Date::Calc qw(Today Add_Delta_Days);

my ($y,$m,$d) = Add_Delta_Days(Today(),-1);
print "Yesterday was $d-$m-$y\n"'

TB0ne · 03-31-2011, 06:33 PM

Quote:

Originally Posted by smallpond

A better Perl function is:

#!/usr/bin/perl
use Date::Calc qw(Today Add_Delta_Days);

my ($y,$m,$d) = Add_Delta_Days(Today(),-1);
print "Yesterday was $d-$m-$y\n"'

+1 for smallpond. I agree...the Date::Calc function in Perl is awesome. It even works across years, and calculates leap years automatically. So if you ask it what the date was 5 days ago on January 3, it'll tell you Dec 29th, last year.