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Perl Lecture Notes - May 4, 2002

• Coming Attractions - XML and lots of other acronyms
  • XML processing :
    • roll-your-own using regexps
    • CPAN modules, SAX/DOM, files/streams
    • connecting XML with SQL and relational-databases
    • overview of other XML CPAN modules
  • AxKit : XML to HTML content conversion within apache mod_perl
  • SOAP-Lite : remote procedure calls in an XML format
  • server performance and benchmarking (?)
  • perhaps other Perl specifics, like Perl6 and parrot
  • other topics?

• Today - perl GUI and yet another server/client database
  • Why look a Graphical User application at all in a network course?
  • Answer 1 - It's a cool thing you can do with perl.
  • Answer 2 - Such applications can be a nice implement server backend admininstration tool, or even network client tool. Especially when they're not all that hard to write.

• Perl/Tk
  • based on Tcl/Tk , an open source language / window tool kit
  • library of window widgets to create GUI on unix and Microsoft Windows (see ActiveState's site).
  • Installation:
    perl -MCPAN -e shell; force install Tk
    or similar with ActiveState's "ppm" command on MSWindows
  • Originally written for X (X11) windows, and that's the way I'll show it here. In that environment, you can have the windows pop up on a remote machine, either by
    • setting an ENV variable, i.e. DISPLAY=your.machine.com:0.0
      (which isn't working under ssh on bob right now), or
    • invoking the application with " ./script -display your.machine.com:0.0" on the command line.
    (You may also have to config your machine with an "xhost +remote.ip.com" command or the equivalent to authorize the remote X server to pop up windows on your terminal. Typically you only need do this once.)
  • Note that you do *not* need X11 to run this on MSWindows - you only need X11 if you want to run remote applications as GUI's on your local machine. See for example http://sources.redhat.com/win32-x11/ - an x11 windows thing on win32.
  • To see if X is working, type "xclock -display your.machine.com:0.0" at the command line.
  • Trivial example: Hello World
    • commandline: tk/xHello -display your.machine.com:0.0
    • source
  • Basic ideas:
    • GUI is made up of "widgets" (buttons, labels, textboxes, frames)
    • widgets include Frames which contain other widgets
    • outermost is "MainWindow"; all others created from this
    • very similar to Java SWING stuff and other GUI frameworks
    • each widget is places spacially with a layout manager using "pack", "grid", or "place" methods.
    • all methods take -option=>value pairs to define their characterstics.
    • There are *many* various widgets, options, and methods.
    • All have $widget->configure(-option=>value) method to change things.
    • Most of the calls return the object, so you can often (if you like) chain the method calls:
        $mainwindow->Button()->pack()
      rather than
        $b=$mainwind->Button; $b->pack;
    • Typically the widgets do things by either
      (1) callback subroutines and/or (2) perl variables bound to their internal values
    • (Note: this "callback" method of programming is also what is used in typical XML stream processing...)
  • Examples:
    • xTimer (source)
    • widget (installed as /usr/bin/widget as part of Perl/Tk)
      • bouncing balls
      • Gedi text editor
      • browse through others
    • ptkdb - a graphical interface to the debugger (Devel::ptkdb)
      see files in ptkdb directory

• a bit about LDAP and how to call it from Perl
  • A specialized server/client database optimized reading and searching.
  • Structure is a tree of "Entries", each with various attributes.
  • Tuned to give quick response to high-volume lookup.
  • Authentication and database replication supported. (Though not trivial to turn on...)
  • Commonly used for something like an organization's user database.
  • config file and schema define "attributes" (properties of an entry) and "classes" (template of which attributes an entry may or must have)
  • These are worldwide, standard definitions - and they're pretty persickity.
  • pictures of LDAP trees
    • from openldap docs
    • tree structure on bob
  • Installation notes and some config files on bob
    • Installation
    • slapd.conf
    • inetOrgPerson.schema
  • Net::LDAP is one of a number of perl CPAN modules that query and change LDAP directories.
    • Installation: perl -MCPAN -e shell; install Bundle::Net::LDAP
    • Pretty straightforward perl objects and methods; see examples and resources
  • some perl scripts
    • add a person to the database - source
    • search the database - source
  • LDAP can be (and is) used for site-wide authentication and similar tasks.
  • BTW, here's a java GUI tool for browsing and editing LDAP trees

• Resources / Documentation
  • acronyms
  • Perl/Tk
    • perltk.org
    • Tk at ActiveState
    • Tk POD
    • a tutorial
    • book Learning Perl/Tk by Nancy Walsh
  • LDAP
    • openldap.org
    • Perl-LDAP
    • Programming with Net::LDAP (slides of talk by author)
    • SASL (an authentication protocol I tried to get working this week. But...)

• Assignmnent
  • Read about Perl/Tk and LDAP from the links above.
  • Write a perl GUI applet that displays users and emails from the LDAP user database on bob.
    • If time allows and the spirit moves you, teach it to edit and add entries, too.
    • You may do this entirely on the grad center linux boxes and/or bob, or you can install Perl/Tk on a home machine and run the GUI application as a client that connects across the net to bob.

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