Shell Programming and Scripting

#!/etc/edi/bin/perl -w
 use Date::Manip;
 use Time::Local;
  my ($mt, $dt, $yr, $sec, $wk_st, $wk_nd, $st_date, $nd_date);
   
   (@ARGV != 1) && die "Invalid parameters. Enter date in mm/dd/yyyy format. Exiting";
   ($ARGV[0] !~ /^(0[1-9]|1[012])\/(0[1-9]|[12][0-9]|3[01])\/[\d]{4}$/)
   && die "Invalid date format. Enter date in mm/dd/yyyy. Exiting";
    
    $mt = substr $ARGV[0], 0, 2;
    $dt = substr $ARGV[0], 3, 2;
    $yr = substr $ARGV[0], 6, 4;
     
$s=`cal $mt $yr | head -3 | tail -1`;
$s =~ s/^\s+//;
$sd=substr($s,0,1);
print "current month start date: $mt/$sd/$yr";
print "\n";
$e=`cal $mt $yr | tail -2 | head -1`;
$e =~ s/\s+$//;
$ed=substr($e,-2,2);
print "Current month end date: $mt/$ed/$yr";
print "\n";
$mn=$mt+1;
$yn=$yr;
$mt=$mt-1;
if ( $mt == 0 )
  {
   $mt =12;
   $yr=$yr-1;
}

$ps=`cal $mt $yr | head -3 | tail -1`;
$ps =~ s/^\s+//;
$psd=substr($ps,0,1);
print "previous month start date: $mt/$psd/$yr";
print "\n";
$es=`cal $mt $yr | tail -2 | head -1`;
$es =~ s/\s+$//;
$ees=substr($es,-2,2);
print "prevoius end date: $mt/$ees/$yr";
print "\n";
if ( $mn == 13 )
  {
   $mn =1;
   $yn=$yn+1;
}

$ns=`cal $mn $yn | head -3 | tail -1`;
$ns =~ s/^\s+//;
$nsd=substr($ns,0,1);
print "next month start date: $mn/$nsd/$yn";
print "\n";
$nes=`cal $mn $yn | tail -2 | head -1`;
$nes =~ s/\s+$//;
$nees=substr($nes,-2,2);
print "next month end date: $mn/$nees/$yn";

C:\>
C:\> REM the script
 
C:\> type date_arithmetic.pl
#!perl -w
# Usage: perl date_arithmetic.pl YYYY MM DD
use strict;
use DateTime;
 
# Takes as arguments:
#  - The date
#  - The target day (1 is Monday, 7 Sunday)
#  - The day that we want to call the start of the week (1 is Monday, 7 Sunday)
sub get_day_in_same_week {
  my ($dt, $target, $start_of_week) = @_;
 
  # Work out what day the date is within the (corrected) week
  my $wday = ($dt->day_of_week() - $start_of_week + 7) % 7;
 
  # Correct the argument day to our week
  $target = ($target - $start_of_week + 7) % 7;
 
  # Then adjust the current day
  return $dt->clone()->add(days => $target - $wday);
}
 
my ($yr, $mt, $dt) = @ARGV;
my $dt1 = DateTime->new (
   year   => $yr,
   month  => $mt,
   day    => $dt
);
 
print "Given date         = ", $dt1->ymd,"\n";
print "Start of the week  = ", get_day_in_same_week($dt1, 1, 1)->ymd,"\n";
print "End   of the week  = ", get_day_in_same_week($dt1, 7, 1)->ymd,"\n";
print "First day of month = ", DateTime->new( year => $yr, month => $mt, day => 1 )->ymd,"\n";
print "Last  day of month = ", DateTime->last_day_of_month( year => $yr, month => $mt )->ymd,"\n";
 
C:\>
C:\> REM a few test runs...
C:\> perl date_arithmetic.pl 2011 12 22
Given date         = 2011-12-22
Start of the week  = 2011-12-19
End   of the week  = 2011-12-25
First day of month = 2011-12-01
Last  day of month = 2011-12-31
 
C:\>
C:\> perl date_arithmetic.pl 2011 7 1
Given date         = 2011-07-01
Start of the week  = 2011-06-27
End   of the week  = 2011-07-03
First day of month = 2011-07-01
Last  day of month = 2011-07-31
 
C:\>
C:\> perl date_arithmetic.pl 2011 2 4
Given date         = 2011-02-04
Start of the week  = 2011-01-31
End   of the week  = 2011-02-06
First day of month = 2011-02-01
Last  day of month = 2011-02-28
 
C:\>
C:\> perl date_arithmetic.pl 2012 2 27
Given date         = 2012-02-27
Start of the week  = 2012-02-27
End   of the week  = 2012-03-04
First day of month = 2012-02-01
Last  day of month = 2012-02-29
 
C:\>
C:\> perl date_arithmetic.pl 2011 1 1
Given date         = 2011-01-01
Start of the week  = 2010-12-27
End   of the week  = 2011-01-02
First day of month = 2011-01-01
Last  day of month = 2011-01-31
 
C:\>
C:\>