FAQ 3.5 How do I debug my Perl programs?

Discussion in 'Perl Misc' started by PerlFAQ Server, Feb 16, 2011.

  1. This is an excerpt from the latest version perlfaq3.pod, which
    comes with the standard Perl distribution. These postings aim to
    reduce the number of repeated questions as well as allow the community
    to review and update the answers. The latest version of the complete
    perlfaq is at http://faq.perl.org .

    --------------------------------------------------------------------

    3.5: How do I debug my Perl programs?

    (contributed by brian d foy)

    Before you do anything else, you can help yourself by ensuring that you
    let Perl tell you about problem areas in your code. By turning on
    warnings and strictures, you can head off many problems before they get
    too big. You can find out more about these in strict and warnings.

    #!/usr/bin/perl
    use strict;
    use warnings;

    Beyond that, the simplest debugger is the "print" function. Use it to
    look at values as you run your program:

    print STDERR "The value is [$value]\n";

    The "Data::Dumper" module can pretty-print Perl data structures:

    use Data::Dumper qw( Dumper );
    print STDERR "The hash is " . Dumper( \%hash ) . "\n";

    Perl comes with an interactive debugger, which you can start with the
    "-d" switch. It's fully explained in perldebug.

    If you'd like a graphical user interface and you have "Tk", you can use
    "ptkdb". It's on CPAN and available for free.

    If you need something much more sophisticated and controllable, Leon
    Brocard's "Devel::ebug" (which you can call with the "-D" switch as
    "-Debug") gives you the programmatic hooks into everything you need to
    write your own (without too much pain and suffering).

    You can also use a commercial debugger such as Affrus (Mac OS X), Komodo
    from Activestate (Windows and Mac OS X), or EPIC (most platforms).



    --------------------------------------------------------------------

    The perlfaq-workers, a group of volunteers, maintain the perlfaq. They
    are not necessarily experts in every domain where Perl might show up,
    so please include as much information as possible and relevant in any
    corrections. The perlfaq-workers also don't have access to every
    operating system or platform, so please include relevant details for
    corrections to examples that do not work on particular platforms.
    Working code is greatly appreciated.

    If you'd like to help maintain the perlfaq, see the details in
    perlfaq.pod.
     
    PerlFAQ Server, Feb 16, 2011
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