NAME

    Devel::ebug - A simple, extensible Perl debugger

VERSION

    version 0.64

SYNOPSIS

      use Devel::ebug;
      my $ebug = Devel::ebug->new;
      $ebug->program("calc.pl");
      $ebug->load;
     
      print "At line: "       . $ebug->line       . "\n";
      print "In subroutine: " . $ebug->subroutine . "\n";
      print "In package: "    . $ebug->package    . "\n";
      print "In filename: "   . $ebug->filename   . "\n";
      print "Code: "          . $ebug->codeline   . "\n";
      $ebug->step;
      $ebug->step;
      $ebug->next;
      my($stdout, $stderr) = $ebug->output;
      my $actual_line = $ebug->break_point(6);
      $ebug->break_point(6, '$e == 4');
      $ebug->break_point("t/Calc.pm", 29);
      $ebug->break_point("t/Calc.pm", 29, '$i == 2');
      $ebug->break_on_load("t/Calc.pm");
      my $actual_line = $ebug->break_point_subroutine("main::add");
      $ebug->break_point_delete(29);
      $ebug->break_point_delete("t/Calc.pm", 29);
      my @filenames    = $ebug->filenames();
      my @break_points = $ebug->break_points();
      my @break_points = $ebug->break_points("t/Calc.pm");
      my @break_points = $ebug->break_points_with_condition();
      my @break_points = $ebug->break_points_with_condition("t/Calc.pm");
      my @break_points = $ebug->all_break_points_with_condition();
      $ebug->watch_point('$x > 100');
      my $codelines = $ebug->codelines(@span);
      $ebug->run;
      my $pad  = $ebug->pad;
      foreach my $k (sort keys %$pad) {
        my $v = $pad->{$k};
        print "Variable: $k = $v\n";
      }
      my $v = $ebug->eval('2 ** $exp');
      my( $v, $is_exception ) = $ebug->eval('die 123');
      my $y = $ebug->yaml('$z');
      my @frames = $ebug->stack_trace;
      my @frames2 = $ebug->stack_trace_human;
      $ebug->undo;
      $ebug->return;
      print "Finished!\n" if $ebug->finished;

DESCRIPTION

    A debugger is a computer program that is used to debug other programs.
    Devel::ebug is a simple, extensible Perl debugger with a clean API.
    Using this module, you may easily write a Perl debugger to debug your
    programs. Alternatively, it comes with an interactive debugger, ebug.

    perl5db.pl, Perl's current debugger is currently 2,600 lines of magic
    and special cases. The code is nearly unreadable: fixing bugs and
    adding new features is fraught with difficulties. The debugger has no
    test suite which has caused breakage with changes that couldn't be
    properly tested. It will also not debug regexes. Devel::ebug is aimed
    at fixing these problems and delivering a replacement debugger which
    provides a well-tested simple programmatic interface to debugging
    programs. This makes it easier to build debuggers on top of
    Devel::ebug, be they console-, curses-, GUI- or Ajax-based.

    There are currently two user interfaces to Devel::debug, ebug and
    ebug_http. ebug is a console-based interface to debugging programs,
    much like perl5db.pl. ebug_http is an innovative web-based interface to
    debugging programs.

    Note that if you're debugging a program, you can invoke the debugger in
    the program itself by using the INT signal:

      kill 2, $$ if $square > 100;

    Devel::ebug is a work in progress.

    Internally, Devel::ebug consists of two parts. The frontend is
    Devel::ebug, which you interact with. The frontend starts the code you
    are debugging in the background under the backend (running it under
    perl -d:ebug code.pl). The backend starts a TCP server, which the
    frontend then connects to, and uses this to drive the backend. This
    adds some flexibility in the debugger. There is some minor security in
    the client/server startup (a secret word), and a random port is used
    from 3141-4165 so that multiple debugging sessions can happen
    concurrently.

CONSTRUCTOR

 new

    The constructor creats a Devel::ebug object:

      my $ebug = Devel::ebug->new;

 program

    The program method selects which program to load:

      $ebug->program("calc.pl");

 load

    The load method loads the program and gets ready to debug it:

      $ebug->load;

METHODS

 break_point

    The break_point method sets a break point in a program. If you are
    running through a program, the execution will stop at a break point.
    Break points can be set in a few ways.

    A break point can be set at a line number in the current file:

      my $actual_line = $ebug->break_point(6);

    A break point can be set at a line number in the current file with a
    condition that must be true for execution to stop at the break point:

      my $actual_line = $ebug->break_point(6, '$e = 4');

    A break point can be set at a line number in a file:

      my $actual_line = $ebug->break_point("t/Calc.pm", 29);

    A break point can be set at a line number in a file with a condition
    that must be true for execution to stop at the break point:

      my $actual_line = $ebug->break_point("t/Calc.pm", 29, '$i == 2');

    Breakpoints can not be set on some lines (for example comments); in
    this case a breakpoint will be set at the next breakable line, and the
    line number will be returned. If no such line exists, no breakpoint is
    set and the function returns undef.

 break_on_load

    Set a breakpoint on file loading, the file name can be relative or
    absolute.

 break_point_delete

    The break_point_delete method deletes an existing break point. A break
    point at a line number in the current file can be deleted:

      $ebug->break_point_delete(29);

    A break point at a line number in a file can be deleted:

      $ebug->break_point_delete("t/Calc.pm", 29);

 break_point_subroutine

    The break_point_subroutine method sets a break point in a program right
    at the beginning of the subroutine. The subroutine is specified with
    the full package name:

      my $line = $ebug->break_point_subroutine("main::add");
      $ebug->break_point_subroutine("Calc::fib");

    The return value is the line at which the break point is set.

 break_points

    The break_points method returns a list of all the line numbers in a
    given file that have a break point set.

    Return the list of breakpoints in the current file:

      my @break_points = $ebug->break_points();

    Return the list of breakpoints in a given file:

      my @break_points = $ebug->break_points("t/Calc.pm");

 break_points_with_condition

    The break_points method returns a list of break points for a given
    file.

    Return the list of breakpoints in the current file:

      my @break_points = $ebug->break_points_with_condition();

    Return the list of breakpoints in a given file:

      my @break_points = $ebug->break_points_with_condition("t/Calc.pm");

    Each element of the list has the form

      { filename  => "t/Calc.pm",
        line      => 29,
        condition => "$foo > 12",
        }

    where condition might not be present.

 all_break_points_with_condition

    Like break_points_with_condition but returns a list of break points for
    the whole program.

 codeline

    The codeline method returns the line of code that is just about to be
    executed:

      print "Code: "          . $ebug->codeline   . "\n";

 codelines

    The codelines method returns lines of code.

    It can return all the code lines in the current file:

      my @codelines = $ebug->codelines();

    It can return a span of code lines from the current file:

      my @codelines = $ebug->codelines(1, 3, 4, 5);

    It can return all the code lines in a file:

      my @codelines = $ebug->codelines("t/Calc.pm");

    It can return a span of code lines in a file:

      my @codelines = $ebug->codelines("t/Calc.pm", 5, 6);

 eval

    The eval method evaluates Perl code in the current program and returns
    the result. If the evaluation results in an exception, $@ is returned.

      my $v = $ebug->eval('2 ** $exp');

    In list context, eval also returns a flag indicating if the evaluation
    resulted in an exception.

      my( $v, $is_exception ) = $ebug->eval('die 123');

 filename

    The filename method returns the filename of the currently running code:

      print "In filename: "   . $ebug->filename   . "\n";

 filenames

    The filenames method returns a list of the filenames of all the files
    currently loaded:

      my @filenames = $ebug->filenames();

 finished

    The finished method returns whether the program has finished running:

      print "Finished!\n" if $ebug->finished;

 line

    The line method returns the line number of the statement about to be
    executed:

      print "At line: "       . $ebug->line       . "\n";

 next

    The next method steps onto the next line in the program. It executes
    any subroutine calls but does not step through them.

      $ebug->next;

 output

    The output method returns any content the program has output to either
    standard output or standard error:

      my($stdout, $stderr) = $ebug->output;

 package

    The package method returns the package of the currently running code:

      print "In package: "    . $ebug->package    . "\n";

 pad

      my $pad  = $ebug->pad;
      foreach my $k (sort keys %$pad) {
        my $v = $pad->{$k};
        print "Variable: $k = $v\n";
      }

 return

    The return subroutine returns from a subroutine. It continues running
    the subroutine, then single steps when the program flow has exited the
    subroutine:

      $ebug->return;

    It can also return your own values from a subroutine, for testing
    purposes:

      $ebug->return(3.141);

 run

    The run subroutine starts executing the code. It will only stop on a
    break point or watch point.

      $ebug->run;

 step

    The step method steps onto the next line in the program. It steps
    through into any subroutine calls.

      $ebug->step;

 subroutine

    The subroutine method returns the subroutine of the currently working
    code:

      print "In subroutine: " . $ebug->subroutine . "\n";

 stack_trace

    The stack_trace method returns the current stack trace, using
    Devel::StackTrace. It returns a list of Devel::StackTraceFrame methods:

      my @traces = $ebug->stack_trace;
      foreach my $trace (@traces) {
        print $trace->package, "->",$trace->subroutine,
        "(", $trace->filename, "#", $trace->line, ")\n";
      }

 stack_trace_human

    The stack_trace_human method returns the current stack trace in a
    human-readable format:

      my @traces = $ebug->stack_trace_human;
      foreach my $trace (@traces) {
        print "$trace\n";
      }

 undo

    The undo method undoes the last action. It accomplishes this by
    restarting the process and passing (almost) all the previous commands
    to it. Note that commands which do not change state are ignored.
    Commands that change state are: break_point, break_point_delete,
    break_point_subroutine, eval, next, step, return, run and watch_point.

      $ebug->undo;

    It can also undo multiple commands:

      $ebug->undo(3);

 watch_point

    The watch point method sets a watch point. A watch point has a
    condition, and the debugger will stop running as soon as this condition
    is true:

      $ebug->watch_point('$x > 100');

 yaml

    The eval method evaluates Perl code in the current program and returns
    the result of YAML's Dump() method:

      my $y = $ebug->yaml('$z');

SEE ALSO

    perldebguts

      The guts of debugging Perl

    Devel::Chitin

      A class that exposes the Perl debugging facilities as an API, with
      some functional overlap with Devel::ebug.

    ebug

      Command-line interface to Devel::ebug

    ebug_http

      Web based interface to Devel::ebug

CAVEATS

    Devel::ebug does not support Perls prior to 5.10.1.

    Devel::ebug does not handle signals under Windows.

AUTHOR

    Original author: Leon Brocard <acme@astray.com>

    Current maintainer: Graham Ollis <plicease@cpan.org>

    Contributors:

    Brock Wilcox <awwaiid@thelackthereof.org>

    Taisuke Yamada

COPYRIGHT AND LICENSE

    This software is copyright (c) 2005-2021 by Leon Brocard.

    This is free software; you can redistribute it and/or modify it under
    the same terms as the Perl 5 programming language system itself.

