Extract day of week using perl and mysql date format - mysql

Question

I am looping through a range of consecutive dates. I need to find out which are weekends so they can be discarded. One method would be to determine the day of week via perl (what my script is written in) or query with each pass through the loop. There will never be more than 30 dates, usually 5 or less to check. Would it be more efficient to load up Date::Time and use perl or run a Query without needing modules? If perl is the best method I could use a little help extracting the day of week from the YYYY-MM-DD format. I'd be ok with number 1-7 or shortname mon-sun.
2012-05-01
2012-05-02
2012-05-03
2012-05-04
2012-05-05
2012-05-06
not sure if this is possible but perhaps a more suitable solution would be to write a query (since I know the start and end and they are consecutive) to count days between x and y where dayofweek NOT IN(6,7)

Answer 1

See DateTime::Format::Strptime and DateTime.
use 5.010;
use strictures;
use DateTime::Format::Strptime qw();
my $parser = DateTime::Format::Strptime->new(pattern => '%F');
for my $date (qw(
2012-05-01
2012-05-02
2012-05-03
2012-05-04
2012-05-05
2012-05-06
)) {
my $dow = $parser->parse_datetime($date)->day_of_week;
say "$date is a weekend day" if 6 == $dow or 7 == $dow;
}

Answer 2

MySQL has a day of week function you can use directly.

Answer 3

The most obvious solution is to use the Time::Piece module, which has been a core module of Perl since v5.9 and so probably doesn't need installing on your system.
The wday method returns a numeric day of week where 1 == Sunday, so for the weekend you are looking for values of 7 (Saturday) or 1. This can be adjusted so that Saturday is represented by zero instead (and Sunday by 1) by writing
my $dow = $tp->wday % 7;
after which the test for a weekend is simply $dow < 2.
Here is some code to demonstrate.
use strict;
use warnings;
use Time::Piece;
while (<DATA>) {
chomp;
my $tp = Time::Piece->strptime($_, '%Y-%m-%d');
my $dow = $tp->wday % 7;
print $_;
print " (weekend)" if $dow < 2;
print "\n";
}
__DATA__
2012-05-01
2012-05-02
2012-05-03
2012-05-04
2012-05-05
2012-05-06
output
2012-05-01
2012-05-02
2012-05-03
2012-05-04
2012-05-05 (weekend)
2012-05-06 (weekend)

Answer 4

You could use the core Time::Local module and then compute the weekday using localtime. Weekday 0 corresponds to Sunday, and 6 is Saturday.
#! /usr/bin/env perl
use strict;
use warnings;
use Time::Local;
my #dates = qw(
2012-05-01
2012-05-02
2012-05-03
2012-05-04
2012-05-05
2012-05-06
);
my #days = qw/ Sun Mon Tue Wed Thu Fri Sat /;
foreach my $date (#dates) {
my($yyyy,$mm,$dd) = split /-/, $date;
my $time_t = timelocal 0, 0, 0, $dd, $mm-1, $yyyy-1900;
my $wday = (localtime $time_t)[6];
my $weekend = ($wday == 0 || $wday == 6) ? " *" : "";
print "$date: $days[$wday] ($wday)$weekend\n";
}
Output:
2012-05-01: Tue (2)
2012-05-02: Wed (3)
2012-05-03: Thu (4)
2012-05-04: Fri (5)
2012-05-05: Sat (6) *
2012-05-06: Sun (0) *
For fun, you could go Swiss Army Chainsaw and scrape the output of the cal utility.
#! /usr/bin/env perl
use strict;
use warnings;
use 5.10.0; # for smart matching
sub weekday_type {
my($date) = #_;
die "$0: unexpected date '$date'"
unless my($yyyy,$mm,$dd) =
$date =~ /^([0-9]{1,4})-([0-9]{1,2})-([0-9]{1,2})$/;
my $calendar = `cal -m $mm $yyyy`;
die "$0: cal -m $mm $yyyy failed" if $?;
for (split /\n/, $calendar) {
if (/^ \s* [0-9]{1,2} (?: \s+ [0-9]{1,2})* \s*$/x) {
my #dates = split;
my #weekend = splice #dates, #dates > 1 ? -2 : -1;
return "weekend" if ($dd+0) ~~ #weekend;
}
}
"weekday";
}
Use it as in
my #dates = qw(
2012-05-01
2012-05-02
2012-05-03
2012-05-04
2012-05-05
2012-05-06
);
my #days = qw/ Sun Mon Tue Wed Thu Fri Sat /;
foreach my $date (#dates) {
my $type = weekday_type $date;
print "$date: $type\n";
}
Output:
2012-05-01: weekday
2012-05-02: weekday
2012-05-03: weekday
2012-05-04: weekday
2012-05-05: weekend
2012-05-06: weekend
I don’t recommend doing it this way in production.

Answer 5

use Date::Simple qw/date/;
use Date::Range;
my ( $start, $end ) = ( date('2012-05-02'), date('2012-05-16') );
my $range = Date::Range->new( $start, $end );
my #all_dates = $range->dates;
foreach my $d (#all_dates) {
my $date = Date::Simple->new($d);
print $date->day_of_week." ".$d."<br />";
}
#--OUTPUT--#
3 2012-05-02
4 2012-05-03
5 2012-05-04
6 2012-05-05
0 2012-05-06
1 2012-05-07
2 2012-05-08
3 2012-05-09
4 2012-05-10
5 2012-05-11
6 2012-05-12
0 2012-05-13
1 2012-05-14
2 2012-05-15
3 2012-05-16