#!/usr/bin/perl

#
# Perl Process Killer (PPK)
# ppk {process name, reqired} {iterations, optional}
#

use strict;
use warnings;

my $loop = -1;
my @immortal;
my $flags;
my $process;
my $id;
my $only_one = 0;
my @level = qw/1 2 3 15 9 -9/;

sub check_match
{
  die "ACK, GASP:  $id failed to match on $_[0]" if( (not $only_one) && ((not defined $_[1]) || (not defined $_[2])) );
  die "ACK, GASP:  $id failed to match on $_[0]" if($only_one && (not defined $_[1]));
}

die "ACK, GASP:  Need program name to search for!\n"
  if( (not defined $ARGV[0]) || ($ARGV[0] =~ m/^\s*\d+\s*$/) );
# Other operating systems can be supported, I just do not have access to them
# to configure $^O, $flags, $process, and $id properly.
# $^O should be matched against the platform you wish to add support for
# $flags must be set so "ps $flags" returns (at least) the User ID, Process ID, and Command Name
# $process is a regexp that matches against the Command Name
# $id is a regexp that matches the User ID and Process ID; putting them into $1 and $2, respectivly
# Also, don't forget to anchor your $process and $id matches!
if($^O =~ m/linux/i)
{
  $flags = "-ea";
  eval { $process = qr/\s+(?:\d+[:])+?\d+\s+.*?$ARGV[0].*?\s*$/; };
  if($@)
  {
    $@ =~ s/\s+at\s+.*?$0.*$//i;
    die "ACK, GASP:  \"$ARGV[0]\" is an invalid command line argument:\n" .
        "            $@";
  }
  $id = qr/^\s*(\d+)\s+/;
  $only_one = 1;
}
elsif($^O =~ m/irix/i)
{
  $flags = "-eaf";
  eval { $process = qr/\s+(?:\d+[:])+?\d+\s+.*?$ARGV[0].*?\s*$/; };
  if($@)
  {
    $@ =~ s/\s+at\s+.*?$0.*$//i;
    die "ACK, GASP:  \"$ARGV[0]\" is an invalid command line argument:\n" .
        "            $@";
  }
  $id = qr/^\s*(\w+)\s+(\d+)\s+/;
}
else  # Provide crippled functionality...
{
  $flags = "";
  eval { $process = qr/\d+\s+.*?$ARGV[0].*?\s*$/; };
  if($@)
  {
    $@ =~ s/\s+at\s+.*?$0.*$//i;
    die "ACK, GASP:  \"$ARGV[0]\" is an invalid command line argument:\n" .
        "            $@";
  }
  $id = qr/^\s*(\d+)\s+/;
  $only_one = 1;
}

if( (defined $ARGV[1]) && !($ARGV[1] =~ m/\D/o) && ($ARGV[1] > 0) ) { $loop = int($ARGV[1]); }

my $login = (getpwuid($>))[0] || getlogin() || (getpwuid($<))[0];
while($loop != 0)
{
  $loop-- if($loop > 0);
  foreach (map { $_->[0] }
           sort { $b->[1] <=> $a->[1] } 
           map { m/$id/;
                 check_match($_, $1, ((not $only_one) ? $2 : ""));
                 [$_, ((not $only_one) ? $2 : $1)] }
           grep { m/$process/ } `ps $flags`)
  {
    m/$id/;
    check_match($_, $1, ((not $only_one) ? $2 : ""));
    next if( ((not $only_one) && ($1 ne $login) && ($login ne "root"))
               ||
             (((not $only_one) ? $2 : $1) == $$)
               ||
             (scalar grep { ((not $only_one) ? $2 : $1) == $_ } @immortal) );
    my $successful = 0;
    foreach (@level)
    {
      if((kill $_, ((not $only_one) ? $2 : $1)) >= 1)
      {
        $successful = 1;
        last;
      }
    }
    if(not $successful)
    {
      warn "WARNING:  I cannot kill PID " . ((not $only_one) ? $2 : $1) . "!\n";
      push @immortal, ((not $only_one) ? $2 : $1);
    }
  }
  sleep(1) if($loop != 0);
}