#!/usr/local/bin/perl

##########################################################################
#
# scheduled.pl
#
# reads the crontab for the current user and provides a listing
# of what's scheduled to run today, or on a specified date
#
# Note: using a date parameter might not work correctly on an x86 machine
##########################################################################

use strict;
use Time::Local;
use POSIX;

my $currentuser = $ENV{LOGNAME};

my $parameter = $ARGV[0];
if ($parameter eq '-h') {usage();}
if ($parameter ne '')
{
  if ($parameter !~ /^\d{4}\/\d{2}\/\d{2}$/)
  {
    print "\nBad date parameter - please supply in the form of MMMM/DD/YY\n\n";
    exit(-1);
  }
}

my ($sorthour, $sortmin, $cronline, $today, $tday, $tmonth);
my (@sortlines, @sortedlines, @taskpieces);

my @lines = ();
my @cronlines = `crontab -l`;

my $todayword = "today ";
my $firstone = 1;
my $oldhour = '99';

### "create" today's date
my ($sec, $min, $hour, $inday, $inmonth, $year, $inwday, $yday, $isdst) = localtime;
$inmonth++;
$today = sprintf ("%4.4d/%2.2d/%2.2d", $year+1900, $inmonth, $inday);

if ($parameter ne '')
{
  $today = $parameter;
  $todayword = '';
  $year =    substr($today, 0, 4);
  $inmonth = substr($today, 5, 2);
  $inday =   substr($today, 8, 2);

  # "catalytic" conversion to get the day of the week
  my $time = timelocal('10','10','10', $inday, $inmonth-1, $year);
  ($sec, $min, $hour, $inday, $inmonth, $year, $inwday) = localtime($time);
  $inmonth++;
}

if (length($inmonth) == 1) {$inmonth = sprintf("%2.2d", $inmonth);}
if (length($inday) == 1)   {$inday   = sprintf("%2.2d", $inday);}
if (length($inwday) == 1)  {$inwday  = sprintf("%2.2d", $inwday);}

my $headerline = "\nScheduled to run $todayword($today) as user <<$currentuser>>:\n\n";

# get relevant schedule lines from crontab
foreach my $line (@cronlines)
{
  chomp $line;
  if ($line !~ /^#/) {push @lines, $line;}
}

# process the relevant crontab lines
foreach my $line (@lines)
{
  my ($cmin, $chour, $cday, $cmonth, $cwday, @taskpieces) = split ' ', $line;
  my ($daymatch, $monthmatch);
  $daymatch = $monthmatch = 0;

  # if it absolutely runs every day, we want it
  if (($cday eq '*') and ($cwday eq '*')) {$daymatch = 1; $monthmatch = 1;}
  else
  {
    # if any day of the month, check specific day of the week
    if ($cday eq '*')
    {
      if (length($cwday) == 1) {$tday = sprintf("%2.2d", $cwday);}
      if ($tday eq $inwday) {$daymatch = 1;}
      elsif ($cwday =~ /,/) {$daymatch = docommacheck($cwday, $inwday);}
      elsif ($cwday =~ /-/) {$daymatch = dodashcheck($cwday, $inwday);}
    }
    else   # if any day of the week, check specific day of the month
    {
      if (length($cday) == 1) {$tday = sprintf("%2.2d", $cday);}
      if ($tday eq $inday) {$daymatch = 1;}
      elsif ($cday =~ /,/) {$daymatch = docommacheck($cday, $inday);}
      elsif ($cday =~ /-/) {$daymatch = dodashcheck($cday, $inday);}
    }

    # check the month
    if (($cmonth eq "*") or ($cmonth eq $inmonth)) {$monthmatch = 1;}
    else
    {
      if (length($cmonth) == 1) {$tmonth = sprintf("%2.2d", $cmonth);}
      if ($tmonth eq $inmonth) {$monthmatch = 1;}
      if    ($cmonth =~ /,/)   {$monthmatch = docommacheck($cmonth, $inmonth);}
      elsif ($cmonth =~ /-/)   {$monthmatch = dodashcheck($cmonth, $inmonth);}
    }
  }

  # if it runs today, store for output
  if ($monthmatch and $daymatch)
  {
    $sorthour = prepforsort($chour);
    $sortmin = prepforsort($cmin);
    push @sortlines, "$sorthour`$sortmin`$line";
  }
}

# sort implicitly by time and output the jobs
@sortedlines = sort{$a cmp $b} @sortlines;
foreach my $templine (@sortedlines)
{
  (undef, undef, $cronline) = split '`', $templine;
  my ($cmin, $chour, $cday, $cmonth, $cwday, @taskpieces) = split ' ', $cronline;

  if ($firstone) {print $headerline;}

  $chour = expand($chour);
  $cmin = expand($cmin);

  # put a blank line between different hours and output the data
  if (($chour ne $oldhour) and ($oldhour ne '99') and (!$firstone))
    {print "\n";}
  print "Hour:$chour  Min:$cmin   \n   ";
  foreach my $task (@taskpieces) {print "$task ";}
  print "\n";

  $oldhour = $chour;
  $firstone = 0;
}


sub docommacheck()
# check each element of a "comma" list
{
  my ($specword, $checkthis) = @_;
  my ($spec, $specmatch, @speclist);
  $specmatch = 0;

  @speclist = split ',', $specword;
  foreach $spec (@speclist) {if (length($spec) == 1) {$spec = sprintf("%2.2d", $spec);}}
  foreach $spec (@speclist) {if ($spec == $checkthis) {$specmatch = 1;}}
  return $specmatch;
}


sub dodashcheck()
# check each element of a "dash" list
{
  my ($specword, $checkthis) = @_;
  my ($spec, $specmatch, @speclist);
  $specmatch = 0;

  @speclist = split '-', $specword;
  for (my $idx=$speclist[0]; $idx<=$speclist[1]; $idx++)
  {
    $spec = sprintf("%2.2d", $idx);
    if ($spec == $checkthis) {$specmatch = 1;}
  }
  return $specmatch;
}


sub expand()
# expand the data if it's a dash list, i.e., 7-12 becomes 7,8,9,10,11,12
# also expand all parameters to two digits, i.e., 7 becomes 07.
# done for consistent output
{
  my ($inlist) = @_;

  my @list;
  my $outlist = '';

  if ($inlist =~ /,/)
  {
    @list = split ',', $inlist;
    foreach my $piece (@list)
      {if (length($piece) == 1) {$piece = sprintf("%2.2d", $piece);}}
    $outlist = join ',', @list;
  }
  elsif ($inlist =~ /-/)
  {
    @list = split '-', $inlist;
    for (my $idx=$list[0]; $idx<=$list[1]; $idx++)
      {$outlist .= sprintf("%2.2d,", $idx);}
    chop($outlist);
  }
  else
  {
    if ((length($inlist) == 1) and ($inlist ne "*")) {$inlist = sprintf("%2.2d", $inlist);}
    $outlist = $inlist;
  }
  return $outlist;
}


sub prepforsort()
# create normalized hour and minute for output sorting
{
  my ($rawvar) = @_;

  if (length($rawvar) == 1) {$rawvar = sprintf("%2.2d", $rawvar);}
  elsif ((substr($rawvar,0,1) =~ /^\d+$/) and (substr($rawvar,1,1) !~ /^\d+$/))
    {$rawvar = sprintf("%2.2d", $rawvar);};
  $rawvar = sprintf("%-100.100s", $rawvar);
  return $rawvar;
}


sub usage()
{
  printf ("\nUsage: scheduled.pl [ (no parameter) | -h | mmmm/dd/yy ]\n");
  printf ("       Indicates what's scheduled to run today as user <$currentuser>.\n");
  printf ("       This is the normal behavior when no parameter is supplied.\n");
  printf ("       program -h displays this text.\n");
  printf ("       Supplying a date in the specified format will run this program\n");
  printf ("       for that date. In that case, the results can NOT be assumed\n");
  printf ("       to be reliable, as the contents of the crontab file may <have been>\n");
  printf ("       or <will be> different on that date.\n\n");
  exit(0);
}