About Us Documentation

Contact Site Map
 

  

WinPak
Documentation

Man Page for PERLDEBUG



NAME
     perldebug - Perl debugging

DESCRIPTION
     First of all, have you tried using the -w switch?

     Debugging

     If you invoke Perl with a -d switch, your script will be run
     under the debugger.  However, the Perl debugger is not a
     separate program as it is in a C environment.  Instead, the
     -d flag tells the compiler to insert source information into
     the pseudocode it's about to hand to the interpreter.  (That
     means your code must compile correctly for the debugger to
     work on it.)  Then when the interpreter starts up, it pre-
     loads a Perl library file containing the debugger itself.
     The program will halt before the first executable statement
     (but see below) and ask you for one of the following
     commands:

     h           Prints out a help message.

     T           Stack trace.  If you do bizarre things to your
                 @_ arguments in a subroutine, the stack
                 backtrace will not always show the original
                 values.

     s           Single step.  Executes until it reaches the
                 beginning of another statement.

     n           Next.  Executes over subroutine calls, until it
                 reaches the beginning of the next statement.

     f           Finish.  Executes statements until it has
                 finished the current subroutine.

     c           Continue.  Executes until the next breakpoint is
                 reached.

     c line      Continue to the specified line.  Inserts a one-
                 time-only breakpoint at the specified line.

     <CR>        Repeat last n or s.

     l min+incr  List incr+1 lines starting at min.  If min is
                 omitted, starts where last listing left off.  If
                 incr is omitted, previous value of incr is used.

     l min-max   List lines in the indicated range.

     l line      List just the indicated line.



     l           List next window.

     -           List previous window.

     w line      List window (a few lines worth of code) around
                 line.

     l subname   List subroutine.  If it's a long subroutine it
                 just lists the beginning.  Use "l" to list more.

     /pattern/   Regular expression search forward in the source
                 code for pattern; the final / is optional.

     ?pattern?   Regular expression search backward in the source
                 code for pattern; the final ? is optional.

     L           List lines that have breakpoints or actions.

     S           Lists the names of all subroutines.

     t           Toggle trace mode on or off.

     b line [ condition ]
                 Set a breakpoint.  If line is omitted, sets a
                 breakpoint on the line that is about to be
                 executed.  If a condition is specified, it is
                 evaluated each time the statement is reached and
                 a breakpoint is taken only if the condition is
                 true.  Breakpoints may only be set on lines that
                 begin an executable statement.  Conditions don't
                 use if:

                     b 237 $x > 30
                     b 33 /pattern/i


     b subname [ condition ]
                 Set breakpoint at first executable line of
                 subroutine.

     d line      Delete breakpoint.  If line is omitted, deletes
                 the breakpoint on the line that is about to be
                 executed.

     D           Delete all breakpoints.

     a line command
                 Set an action for line.  A multiline command may
                 be entered by backslashing the newlines.  This
                 command is Perl code, not another debugger
                 command.



     A           Delete all line actions.

     < command   Set an action to happen before every debugger
                 prompt.  A multiline command may be entered by
                 backslashing the newlines.

     > command   Set an action to happen after the prompt when
                 you've just given a command to return to
                 executing the script.  A multiline command may
                 be entered by backslashing the newlines.

     V package [symbols]
                 Display all (or some) variables in package
                 (defaulting to the main package) using a data
                 pretty-printer (hashes show their keys and
                 values so you see what's what, control
                 characters are made printable, etc.).  Make sure
                 you don't put the type specifier (like $) there,
                 just the symbol names, like this:

                     V DB filename line


     X [symbols] Same as as "V" command, but within the current
                 package.

     ! number    Redo a debugging command.  If number is omitted,
                 redoes the previous command.

     ! -number   Redo the command that was that many commands
                 ago.

     H -number   Display last n commands.  Only commands longer
                 than one character are listed.  If number is
                 omitted, lists them all.

     q or ^D     Quit.  ("quit" doesn't work for this.)

     command     Execute command as a Perl statement.  A missing
                 semicolon will be supplied.

     p expr      Same as print DB::OUT expr.  The DB::OUT
                 filehandle is opened to /dev/tty, regardless of
                 where STDOUT may be redirected to.

     Any command you type in that isn't recognized by the
     debugger will be directly executed (eval'd) as Perl code.
     Leading white space will cause the debugger to think it's
     NOT a debugger command.

     If you have any compile-time executable statements (code
     within a BEGIN block or a use statement), these will NOT be


     stopped by debugger, although requires will.  From your own
     code, however, you can transfer control back to the debugger
     using the following statement, which is harmless if the
     debugger is not running:

         $DB::single = 1;


     Customization

     If you want to modify the debugger, copy perl5db.pl from the
     Perl library to another name and modify it as necessary.
     You'll also want to set environment variable PERL5DB to say
     something like this:

         BEGIN { require "myperl5db.pl" }

     You can do some customization by setting up a .perldb file
     which contains initialization code.  For instance, you could
     make aliases like these (the last one in particular most
     people seem to expect to be there):

         $DB::alias{'len'} = 's/^len(.*)/p length($1)/';
         $DB::alias{'stop'} = 's/^stop (at|in)/b/';
         $DB::alias{'.'} = 's/^./p '
                         . '"\$DB::sub(\$DB::filename:\$DB::line):\t"'
                         . ',\$DB::dbline[\$DB::line]/' ;


     Other resources

     You did try the -w switch, didn't you?

BUGS
     If your program exit()s or die()s, so does the debugger.

     There's no builtin way to restart the debugger without
     exiting and coming back into it.  You could use an alias
     like this:

         $DB::alias{'rerun'} = 'exec "perl -d $DB::filename"';

     But you'd lose any pending breakpoint information, and that
     might not be the right path, etc.


 

 

Email addresses listed on this site may  NOT be used for unsolicited commercial email.

Ready-to-Run Software, Inc Privacy Statement

Portions (c)Copyright, 1996-2005 by Ready-to-Run Software, Inc
(All rights reserved.)
212 Cedar Cove
Lansing, NY 14882
Phone: 607 533 UNIX (8649)
Fax: 607 533 4002