Devel::ptkdb(3) Perl debugger using a Tk GUI


  ptkdb is a debugger for perl that uses perlTk for a user interface.
  Features include:
    Hot Variable Inspection
    Breakpoint Control Panel
    Expression List
    Subroutine Tree


To debug a script using ptkdb invoke perl like this:

perl -d:ptkdb


    perl -d:ptkdb

Code Pane

Line Numbers
 Line numbers are presented on the left side of the window. Lines that
 have lines through them are not breakable. Lines that are plain text
 are breakable. Clicking on these line numbers will insert a
 breakpoint on that line and change the line number color to
 $ENV{'PTKDB_BRKPT_COLOR'} (Defaults to Red). Clicking on the number
 again will remove the breakpoint.  If you disable the breakpoint with
 the controls on the BrkPt notebook page the color will change to
Cursor Motion
If you place the cursor over a variable (i.e. $myVar, @myVar, or %myVar) and pause for a second the debugger will evaluate the current value of the variable and pop a balloon up with the evaluated result. This feature is not available with Tk400.

If Data::Dumper(standard with perl5.00502)is available it will be used to format the result. If there is an active selection, the text of that selection will be evaluated.

Notebook Pane

 This is a list of expressions that are evaluated each time the
 debugger stops. The results of the expresssion are presented
 hierarchically for expression that result in hashes or lists.  Double
 clicking on such an expression will cause it to collapse; double
 clicking again will cause the expression to expand. Expressions are
 entered through B<Enter Expr> entry, or by Alt-E when text is
 selected in the code pane.
 The B<Quick Expr> entry, will take an expression, evaluate it, and
 replace the entries contents with the result.  The result is also
 transfered to the 'clipboard' for pasting.
 Displays a list of all the packages invoked with the script
 heirarchially. At the bottom of the heirarchy are the subroutines
 within the packages.  Double click on a package to expand
 it. Subroutines are listed by their full package names.
 Presents a list of the breakpoints current in use. The pushbutton
 allows a breakpoint to be 'disabled' without removing it. Expressions
 can be applied to the breakpoint.  If the expression evaluates to be
 'true'(results in a defined value that is not 0) the debugger will
 stop the script.  Pressing the 'Goto' button will set the text pane
 to that file and line where the breakpoint is set.  Pressing the
 'Delete' button will delete the breakpoint.


File Menu

Presents a dialog box telling you about the version of ptkdb. It recovers your OS name, version of perl, version of Tk, and some other information
Presents a list of files that are part of the invoked perl script. Selecting a file from this list will present this file in the text window.
Save Config...
Requires Data::Dumper. Prompts for a filename to save the configuration to. Saves the breakpoints, expressions, eval text and window geometry. If the name given as the default is used and the script is reinvoked, this configuration will be reloaded automatically.

    B<NOTE:>  You may find this preferable to using
Restore Config...
Requires Data::Dumper. Prompts for a filename to restore a configuration saved with the ``Save Config...'' menu item.
Goto Line...
Prompts for a line number. Pressing the ``Okay'' button sends the window to the line number entered. item Find Text...

Prompts for text to search for. Options include forward search, backwards search, and regular expression searching.

 Causes the debugger and the target script to exit.

Control Menu

The debugger allows the script to run to the next breakpoint or until the script exits. item Run To Here

Runs the debugger until it comes to wherever the insertion cursor in text window is placed.

Set Breakpoint
Sets a breakpoint on the line at the insertion cursor. item Clear Breakpoint

Remove a breakpoint on the at the insertion cursor.

Clear All Breakpoints
Removes all current breakpoints
Step Over
Causes the debugger to step over the next line. If the line is a subroutine call it steps over the call, stopping when the subroutine returns.
Step In
Causes the debugger to step into the next line. If the line is a subroutine call it steps into the subroutine, stopping at the first executable line within the subroutine.
Runs the script until it returns from the currently executing subroutine.
Saves the breakpoints and expressions in a temporary file and restarts the script from the beginning. CAUTION: This feature will not work properly with debugging of CGI Scripts.
Stop On Warning
When "-w" is enabled the debugger will stop when warnings such as, ``Use of uninitialized value at line N'' are encountered. The debugger will stop on the NEXT line of execution since the error can't be detected until the current line has executed.

This feature can be turned on at startup by adding:

$DB::ptkdb::stop_on_warning = 1 ;

to a .ptkdbrc file

Data Menu

Enter Expression
When an expression is entered in the ``Enter Expression:'' text box, selecting this item will enter the expression into the expression list. Each time the debugger stops this expression will be evaluated and its result updated in the list window.
Delete Expression
 Deletes the highlighted expression in the expression window.
Delete All Expressions
 Delete all expressions in the expression window.
Expression Eval Window
Pops up a two pane window. Expressions of virtually unlimitted length can be entered in the top pane. Pressing the 'Eval' button will cause the expression to be evaluated and its placed in the lower pane. If Data::Dumper is available it will be used to format the resulting text. Undo is enabled for the text in the upper pane.

HINT: You can enter multiple expressions by separating them with commas.

Use Data::Dumper for Eval Window
Enables or disables the use of Data::Dumper for formatting the results of expressions in the Eval window.

Stack Menu

Maintains a list of the current subroutine stack each time the debugger stops. Selecting an item from this menu will set the text in the code window to that particular subourtine entry point.

Bookmarks Menu

Maintains a list of bookmarks. The booksmarks are saved in ~/.ptkdb_bookmarks
Add Bookmark
Adds a bookmark to the bookmark list.


Here is a list of the current active XResources options. Several of these can be overridden with environmental variables. Resources can be added to .Xresources or .Xdefaults depending on your X configuration. To enable these resources you must either restart your X server or use the xrdb -override resFile command. xfontsel can be used to select fonts.

    * Perl Tk Debugger XResources.   
    * Note... These resources are subject to change.   
    * Use 'xfontsel' to select different fonts.
    * Append these resource to ~/.Xdefaults | ~/.Xresources
    * and use xrdb -override ~/.Xdefaults | ~/.Xresources
    * to activate them. 
    /* Set Value to se to place scrollbars on the right side of windows 
  CAUTION:  extra whitespace at the end of the line is causing
    failures with Tk800.011.
    sw -> puts scrollbars on left, se puts scrollars on the right
    ptkdb*scrollbars: sw
    /* controls where the code pane is oriented, down the left side, or across the top */
    /* values can be set to left, right, top, bottom */
    ptkdb*codeside: left
    * Background color for the balloon
    * CAUTION:  For certain versions of Tk trailing
    * characters after the color produces an error
    ptkdb.frame2.frame1.rotext.balloon.background: green
    ptkdb.frame2.frame1.rotext.balloon.font: fixed                       /* Hot Variable Balloon Font */
    ptkdb.frame*font: fixed                           /* Menu Bar */
    ptkdb.frame.menubutton.font: fixed                /* File menu */
    ptkdb.frame2.frame1.rotext.font: fixed            /* Code Pane */
    ptkdb.notebook.datapage.frame1.hlist.font: fixed  /* Expression Notebook Page */
    ptkdb.notebook.subspage*font: fixed               /* Subroutine Notebook Page */
    ptkdb.notebook.brkptspage*entry.font: fixed       /* Delete Breakpoint Buttons */
    ptkdb.notebook.brkptspage*button.font: fixed      /* Breakpoint Expression Entries */
    ptkdb.notebook.brkptspage*button1.font: fixed     /* Breakpoint Expression Entries */
    ptkdb.notebook.brkptspage*checkbutton.font: fixed /* Breakpoint Checkbuttons */
    ptkdb.notebook.brkptspage*label.font: fixed       /* Breakpoint Checkbuttons */
    ptkdb.toplevel.frame.textundo.font: fixed         /* Eval Expression Entry Window */
    ptkdb.toplevel.frame1.text.font: fixed            /* Eval Expression Results Window */
    ptkdb.toplevel.button.font:  fixed                /* "Eval..." Button */
    ptkdb.toplevel.button1.font: fixed                /* "Clear Eval" Button */
    ptkdb.toplevel.button2.font: fixed                /* "Clear Results" Button */
    ptkdb.toplevel.button3.font: fixed                /* "Clear Dismiss" Button */
    * Background color for where the debugger has stopped 
    ptkdb*stopcolor: blue
    * Background color for set breakpoints  
    ptkdb*breaktagcolor*background: yellow
    ptkdb*disabledbreaktagcolor*background: white
    * Font for where the debugger has stopped
    ptkdb*stopfont: -*-fixed-bold-*-*-*-*-*-*-*-*-*-*-*
    * Background color for the search tag
    ptkdb*searchtagcolor: green

Environmental Variables

Sets the background color of a set breakpoint
Sets the background color of a disabled breakpoint
Sets the font of the Text in the code pane.
Sets which side the code pane is packed onto. Defaults to 'left'. Can be set to 'left', 'right', 'top', 'bottom'.

Overrides the Xresource ptkdb*codeside: side.

 Sets the font used in the expression notebook page.
 Sets the font used in the Expression Eval Window
 Sets the value used for Data::Dumper 'indent' setting. See man Data::Dumper
 A non-zero value Sets the scrollbars of all windows to be on the
 right side of the window. Useful for Windows users using ptkdb in an
 X environment.
Sets the format of line numbers on the left side of the window. Default value is %05d. useful if you have a script that contains more than 99999 lines.
Sets the X display that the ptkdb window will appear on when invoked. Useful for debugging CGI scripts on remote systems.
Sets the path of the bookmarks file. Default is $ENV{'HOME'}/.ptkdb_bookmarks
Sets the color that highlights the line where the debugger is stopped



If this file is present in ~/ or in the directory where perl is invoked the file will be read and executed as a perl script before the debugger makes its initial stop at startup. There are several 'api' calls that can be used with such scripts. There is an internal variable $DB::no_stop_at_start that may be set to non-zero to prevent the debugger from stopping at the first line of the script. This is useful for debugging CGI scripts.

There is a system ptkdbrc file in $PREFIX/lib/perl5/$VERS/Devel/ptkdbrc

brkpt($fname, @lines)
Sets breakspoints on the list of lines in $fname. A warning message is generated if a line is not breakable.
condbrkpt($fname, @($line, $expr) )
Sets conditional breakpoints in $fname on pairs of $line and $expr. A warning message is generated if a line is not breakable. NOTE: the validity of the expression will not be determined until execution of that particular line.
Sets a breakpoint on each subroutine name listed. A warning message is generated if a subroutine does not exist. NOTE: for a script with no other packages the default package is ``main::'' and the subroutines would be ``main::mySubs''.
Uses the list of @regExprs as a list of regular expressions to set breakpoints. Sets breakpoints on every subroutine that matches any of the listed regular expressions.
textTagConfigure(tag, ?option?, ?value?)
Allows the user to format the text in the code window. The option value pairs are the same values as the option for the tagConfigure method documented in Tk::Text. Currently the following tags are in effect:

    'code'               Format for code in the text pane
    'stoppt'             Format applied to the line where the debugger is currently stopped
    'breakableLine'      Format applied to line numbers where the code is 'breakable'
    'nonbreakableLine'   Format applied to line numbers where the code is no breakable
    'breaksetLine'       Format applied to line numbers were a breakpoint is set
    'breakdisabledLine'  Format applied to line numbers were a disabled breakpoint is set
    'search_tag'         Format applied to text when located by a search.  
 # Turns off the overstrike on lines that you can't set a breakpoint on
 # and makes the text color yellow. 
    textTagConfigure('nonbreakableLine', -overstrike => 0, -foreground => "yellow") ;
Add a list of expressions to the 'Exprs' window. NOTE: use the single quote character \' to prevent the expression from being ``evaluated'' in the string context.

    # Adds the $_ and @_ expressions to the active list
    add_exprs('$_', '@_') ;


Debugging Other perlTk Applications

ptkdb can be used to debug other perlTk applications if some cautions are observed. Basically, do not click the mouse in the application's window(s) when you've entered the debugger and do not click in the debugger's window(s) while the application is running. Doing either one is not necessarily fatal, but it can confuse things that are going on and produce unexpected results.

Be aware that most perlTk applications have a central event loop. User actions, such as mouse clicks, key presses, window exposures, etc will generate 'events' that the script will process. When a perlTk application is running, its 'MainLoop' call will accept these events and then dispatch them to appropriate callbacks associated with the appropriate widgets.

Ptkdb has its own event loop that runs whenever you've stopped at a breakpoint and entered the debugger. However, it can accept events that are generated by other perlTk windows and dispatch their callbacks. The problem here is that the application is supposed to be 'stopped', and logically the application should not be able to process events.

A future version of ptkdb will have an extension that will 'filter' events so that application events are not processed while the debugger is active, and debugger events will not be processed while the target script is active.

Debugging CGI Scripts

One advantage of ptkdb over the builtin debugger(-d) is that it can be used to debug CGI perl scripts as they run on a web server. Be sure that that your web server's perl instalation includes Tk.

Change your

  #! /usr/local/bin/perl


  #! /usr/local/bin/perl -d:ptkdb

TIP: You can debug scripts remotely if you're using a unix based Xserver and where you are authoring the script has an Xserver. The Xserver can be another unix workstation, a Macintosh or Win32 platform with an appropriate X package. In your script insert the following BEGIN subroutine:

    sub BEGIN {
      $ENV{'DISPLAY'} = "myHostname:0.0" ;

Be sure that your web server has permission to open windows on your Xserver (see the xhost manpage).

Access your web page with your browswer and 'submit' the script as normal. The ptkdb window should appear on myHostname's monitor. At this point you can start debugging your script. Be aware that your browser may timeout waiting for the script to run.

To expedite debugging you may want to setup your breakpoints in advance with a .ptkdbrc file and use the $DB::no_stop_at_start variable. NOTE: for debugging web scripts you may have to have the .ptkdbrc file installed in the server account's home directory (~www) or whatever username your webserver is running under. Also try installing a .ptkdbrc file in the same directory as the target script.


Breakpoint Controls
If the size of the right hand pane is too small the breakpoint controls are not visible. The breakpoints are still there, the window may have to be enlarged in order for them to be visible.
Balloons and Tk400
The Balloons in Tk400 will not work with ptkdb. All other functions are supported, but the Balloons require Tk800 or higher.


Andrew E. Page, [email protected]


Matthew Persico For suggestions, and beta testing.


Please report bugs through the following URL: