Arthur Corliss > Paranoid-2.01 > Paranoid::Debug

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Module Version: 2.01   Source   Latest Release: Paranoid-2.04

NAME ^

Paranoid::Debug - Trace message support for paranoid programs

VERSION ^

$Id: lib/Paranoid/Debug.pm, 2.01 2016/06/23 00:34:49 acorliss Exp $

SYNOPSIS ^

  use Paranoid::Debug;

  PDEBUG        = 1;
  PDMAXINDENT   = 40;
  PDPREFIX      = sub { scalar localtime };
  pdebug("starting program", 1);
  foo();

  sub foo {
    pdebug("entering foo()", 2);
    pIn();

    pdebug("someting happened!", 2);

    pOut();
    pdebug("leaving w/rv: $rv", 2):
  }

  pderror("error msg");

DESCRIPTION ^

The purpose of this module is to provide a useful framework to produce debugging output. With this module you can assign a level of detail to pdebug statements, and they'll only be displayed to STDERR when PDEBUG is set to that level or higher. This allows you to have your program produce varying levels of debugging output.

Using the pIn and pOut functions at the beginning and end of each function will cause debugging output to be indented appropriately so you can visually see the level of recursion.

NOTE: All modules within the Paranoid framework use this module. Their debug levels range from 9 and up. You should use 1 - 8 for your own modules or code.

EXPORT TARGETS

Only PDEBUG, pdebug, pIn, and pOut are exported by default. All other functions and constants can be exported with the :all tag set.

SUBROUTINES/METHODS ^

PDEBUG

PDEBUG is an lvalue subroutine which is initially set to 0, but can be set to any positive integer. The higher the number the more pdebug statements are printed.

PDMAXINDENT

PDMAXINDENT is an lvalue subroutine which is initially set to 60, but can be set to any integer. This controls the max indentation of the debug messages. Obviously, it wouldn't help to indent a debug message by a hundred columns on an eighty column terminal just because your stack depth gets that deep.

PDPREFIX

PDPREFIX is also an lvalue subroutine and is set by default to a subroutine that returns as a string the standard prefix for debug messages:

  [PID - DLEVEL] Subroutine:

Assigning another reference to a subroutine or string can override this behavior.

pderror

  pderror("error msg");

This function prints the passed message to STDERR.

pdebug

  pdebug("debug statement", 3);
  pdebug("debug statement: %s %2d %.3f", 3, @values);

This function is called with one mandatory argument (the string to be printed), and an optional integer. This integer is compared against PDEBUG and the debug statement is printed if PDEBUG is equal to it or higher.

The return value is always the debug statement itself. This allows for a single statement to produce debug output and set variables. For instance:

  Paranoid::ERROR = pdebug("Something bad happened!", 3);

As an added benefit you can pass a printf template along with their values and they will be handled appropriately. String values passed as undef will be replaced with the literal string "undef".

One deviation from printf allows you to specify a placeholder which can gobble up any number of extra arguments while still performing the "undef" substituion:

    pdebug("I was passed these values: %s", 3, @values);

pIn

  pIn();

This function causes all subsequent pdebug messages to be indented by one additional space.

pOut

  pOut();

This function causes all subsequent pdebug messages to be indented by one less space.

DEPENDENCIES ^

Paranoid

BUGS AND LIMITATIONS ^

pderror (and by extension, pdebug) will generate errors if STDERR is closed elsewhere in the program.

AUTHOR ^

Arthur Corliss (corliss@digitalmages.com)

LICENSE AND COPYRIGHT ^

This software is licensed under the same terms as Perl, itself. Please see http://dev.perl.org/licenses/ for more information.

(c) 2005 - 2015, Arthur Corliss (corliss@digitalmages.com)

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