#!/usr/bin/perl -w

# process_killer.pl
#
# Interactive process killer utilizing the Tk GUI toolkit.
# Uses the system's "ps" command to get a list of the currently-running processes,
# and the system's "kill" command to send them signals.
#
# My machine's "ps", when run with "ps ux", gives output like the following:
# USER       PID %CPU %MEM   VSZ  RSS TTY      STAT START   TIME COMMAND
# falkkin    531  0.0  1.4  2316 1380 tty1     S    08:53   0:00 -bash
#
# My machine's "kill" is of the form "kill -s $signal $pid".
# Supported signals include TERM, STOP, CONT, INT, HUP, and KILL.
#
# You'll need to modify this script if your "ps" command formats output differently
# or your "kill" command has different syntax.
# Eventually, I hope to make this script more portable.
#
# Authored by Colin McMillen (e-mail: colin at jenovaproject.org) and released
# into the public domain. You may use, copy, redistribute, and modify this program
# without any restrictions.
#
# 
use strict;
use Tk;  

my $VERSION = v0.1;

# Choose the options to send to "ps". Defaults to "ps ux".
my $PS_OPTIONS = $ARGV[0] || "ux";

# Index (starting from 0) of the fields for process ID and command name.
my $PID_FIELD = 1;
my $COMMAND_FIELD = 10;

# Create the main window and add an informational label.
my $top = MainWindow->new(); 
$top->title("process_killer.pl");
$top->Label(text => "Double-click on the process you would like to kill.")->pack();

# Create a frame to hold the process list and its scrollbar.
my $frame1 = $top->Frame()->pack(fill => "both", expand => "y");

# Get the actual process list and discard the first line of output (which 
# contains informational headers that we want to ignore).
my @processes = `ps $PS_OPTIONS`;
shift @processes;

# Use the process list to create a listbox. Add the listbox to $frame1.
my $process_list = $frame1->Listbox(width => 80,
                                    height => 15)->pack(side => "left", 
                                                        fill => "both", 
                                                        expand => "y");

# Split each line of output into fields, based on whitespace. Then, get the
# process ID and command name out of the fields, and add them to the listbox.
foreach my $process (@processes) {
    my (@fields) = split(/\s+/, $process);
    my $pid = $fields[$PID_FIELD];
    my @command = @fields[ $COMMAND_FIELD .. @fields-1 ];
    my $command = join(" ", @command);
    $process_list->insert("end","$pid $command");
}

# Bind a double-click on the listbox to the kill() subroutine.
$process_list->bind("<Double-1>", \&kill);

# Create a scrollbar to scroll the listbox vertically and add it to $frame1.
my $scrollbar = $frame1->Scrollbar(orient  => "vertical",
                                   width   => 10,
                                   command => ["yview", $process_list],
                                   )->pack(side => "left", fill => "y");
$process_list->configure(yscrollcommand => ["set", $scrollbar]);

# Create a frame to hold radiobuttons for choosing a signal.
my $frame2 = $top->Frame()->pack();

# Create the radiobuttons inside $frame2.
$frame2->Label(text => "Choose a signal:")->pack(side => "left");
my $signal = "TERM";
$frame2->Radiobutton(variable => \$signal, 
                     text     => "Terminate", 
                     value    => "TERM")->pack(side => "left");
$frame2->Radiobutton(variable => \$signal, 
                     text     => "Stop", 
                     value    => "STOP")->pack(side => "left");
$frame2->Radiobutton(variable => \$signal, 
                     text     => "Continue", 
                     value    => "CONT")->pack(side => "left");
$frame2->Radiobutton(variable => \$signal,
                     text     => "Interrupt", 
                     value    => "INT")->pack(side => "left");
$frame2->Radiobutton(variable => \$signal, 
                     text     => "Hangup", 
                     value    => "HUP")->pack(side => "left");
$frame2->Radiobutton(variable => \$signal, 
                     text     => "Kill", 
                     value    => "KILL")->pack(side => "left");

# Hand control of the program off to the GUI.
MainLoop();

# Subroutine called when a field in the listbox is double-clicked.
# The process ID of the process is the first field in the listbox's active item.
# The signal to send the process is set by the radiobuttons and stored in
# the variable $signal.
sub kill {
    my $process = $process_list->get('active');
    my ($pid) = split(/ /, $process);
    return unless $pid;
    system("kill -s $signal $pid");
}