1Data::Printer(3) User Contributed Perl Documentation Data::Printer(3)
2
6 Data::Printer - colored pretty-print of Perl data structures and
7 objects
8
10 Want to see what's inside a variable in a complete, colored and human-
11 friendly way?
12 use Data::Printer; # or just "use DDP" for short
14 p @array; # no need to pass references
16 Code above might output something like this (with colors!):
18 [
20 [0] "a",
21 [1] "b",
22 [2] undef,
23 [3] "c",
24 ]
25 You can also inspect objects:
27 my $obj = SomeClass->new;
29 p($obj);
31 Which might give you something like:
33 \ SomeClass {
35 Parents Moose::Object
36 Linear @ISA SomeClass, Moose::Object
37 public methods (3) : bar, foo, meta
38 private methods (0)
39 internals: {
40 _something => 42,
41 }
42 }
43 Data::Printer is fully customizable. If you want to change how things
45 are displayed, or even its standard behavior. Take a look at the
46 available customizations. Once you figure out your own preferences,
47 create a configuration file for yourself and Data::Printer will
48 automatically use it!
49 That's about it! Feel free to stop reading now and start dumping your
51 data structures! For more information, including feature set, how to
52 create filters, and general tips, just keep reading :)
53 Oh, if you are just experimenting and/or don't want to use a
55 configuration file, you can set all options during initialization,
56 including coloring, indentation and filters!
57 use Data::Printer {
59 color => {
60 'regex' => 'blue',
61 'hash' => 'yellow',
62 },
63 filters => {
64 'DateTime' => sub { $_[0]->ymd },
65 'SCALAR' => sub { "oh noes, I found a scalar! $_[0]" },
66 },
67 };
68 The first "{}" block is just syntax sugar, you can safely omit it if it
70 makes things easier to read:
71 use DDP colored => 1;
73 use Data::Printer deparse => 1, sort_keys => 0;
75
77 Here's what Data::Printer has to offer to Perl developers, out of the
78 box:
79 · Very sane defaults (I hope!)
81 · Highly customizable (in case you disagree with me :)
83 · Colored output by default
85 · Human-friendly output, with array index and custom separators
87 · Full object dumps including methods, inheritance and internals
89 · Exposes extra information such as tainted data and weak references
91 · Ability to easily create filters for objects and regular structures
93 · Ability to load settings from a ".dataprinter" file so you don't
95 have to write anything other than "use DDP;" in your code!
96
98 Data::Dumper is a fantastic tool, meant to stringify data structures in
99 a way they are suitable for being "eval"'ed back in.
100 The thing is, a lot of people keep using it (and similar ones, like
102 Data::Dump) to print data structures and objects on screen for
103 inspection and debugging, and while you can use those modules for that,
104 it doesn't mean you should.
105 This is where Data::Printer comes in. It is meant to do one thing and
107 one thing only:
108 display Perl variables and objects on screen, properly formatted (to be
110 inspected by a human)
111 If you want to serialize/store/restore Perl data structures, this
113 module will NOT help you. Try Storable, Data::Dumper, JSON, or
114 whatever. CPAN is full of such solutions!
115
117 Once you load Data::Printer, the "p()" function will be imported into
118 your namespace and available to you. It will pretty-print into STDERR
119 (or any other output target) whatever variable you pass to it.
120 Changing output targets
122 By default, "p()" will be set to use STDERR. As of version 0.27, you
123 can set up the 'output' property so Data::Printer outputs to several
124 different places:
125 · "output => 'stderr'" - Standard error. Same as *STDERR
127 · "output => 'stdout'" - Standard output. Same as *STDOUT
129 · "output => $filename" - Appends to filename.
131 · "output => $file_handle" - Appends to opened handle
133 · "output => \$scalar" - Appends to that variable's content
135 Return Value
137 As of version 0.36, Data::Printer's return value defaults to "pass-
138 through", meaning it will dump the variable to STDERR (or wherever you
139 set the output to) and will return the variable itself.
140 If for whatever reason you want to mangle with the output string
142 instead of printing it, you can either use the (also exported) "np()"
143 function which always returns the string to be printed:
144 use DDP;
146 # move to a string
148 my $string = np @some_array;
149 # send as a warning
151 warn np($some_string);
152 # output to STDOUT instead of STDERR
154 print np(%some_hash);
155 or change the return value to 'dump' and ask for p()'s return value
157 instead: value:
158 use DDP return_value => 'dump';
160 # move to a string
162 my $string = p @some_array;
163 # output to STDOUT instead of STDERR;
165 print p(%some_hash);
166 Note that, in this case, Data::Printer will not colorize the returned
168 string unless you explicitly set the "colored" option to 1:
169 print p(%some_hash, colored => 1); # now with colors!
171 You can - and should - of course, set this during you ""use"" call:
173 use Data::Printer colored => 1;
175 print p( %some_hash ); # will be colored
176 Or by adding the setting to your ".dataprinter" file.
178 As most of Data::Printer, the return value is also configurable. You do
180 this by setting the "return_value" option. There are three options
181 available:
182 · 'dump'
184 p %var; # prints the dump to STDERR (void context)
186 my $string = p %var; # returns the dump *without* printing
187 · 'void':
189 p %var; # prints the dump to STDERR, never returns.
191 my $string = p %var; # $string is undef. Data still printed in STDERR
192 · 'pass' (default as of 0.36):
194 p %var; # prints the dump to STDERR, returns %var
196 my %copy = p %var; # %copy = %var. Data still printed in STDERR
197
199 Below are all the available colorizations and their default values.
200 Note that both spellings ('color' and 'colour') will work.
201 use Data::Printer {
203 color => {
204 array => 'bright_white', # array index numbers
205 number => 'bright_blue', # numbers
206 string => 'bright_yellow', # strings
207 class => 'bright_green', # class names
208 method => 'bright_green', # method names
209 undef => 'bright_red', # the 'undef' value
210 hash => 'magenta', # hash keys
211 regex => 'yellow', # regular expressions
212 code => 'green', # code references
213 glob => 'bright_cyan', # globs (usually file handles)
214 vstring => 'bright_blue', # version strings (v5.16.0, etc)
215 repeated => 'white on_red', # references to seen values
216 caller_info => 'bright_cyan', # details on what's being printed
217 weak => 'cyan', # weak references
218 tainted => 'red', # tainted content
219 escaped => 'bright_red', # escaped characters (\t, \n, etc)
220 # potential new Perl datatypes, unknown to Data::Printer
222 unknown => 'bright_yellow on_blue',
223 },
224 };
225 Don't fancy colors? Disable them with:
227 use Data::Printer colored => 0;
229 By default, 'colored' is set to "auto", which means Data::Printer will
231 colorize only when not being used to return the dump string, nor when
232 the output (default: STDERR) is being piped. If you're not seeing
233 colors, try forcing it with:
234 use Data::Printer colored => 1;
236 Also worth noticing that Data::Printer will honor the
238 "ANSI_COLORS_DISABLED" environment variable unless you force a colored
239 output by setting 'colored' to 1.
240 Remember to put your preferred settings in the ".dataprinter" file so
242 you never have to type them at all!
243
245 Data::Printer provides the nice, short, "p()" function to dump your
246 data structures and objects. In case you rather use a more explicit
247 name, already have a "p()" function (why?) in your code and want to
248 avoid clashing, or are just used to other function names for that
249 purpose, you can easily rename it:
250 use Data::Printer alias => 'Dumper';
252 Dumper( %foo );
254
256 I tried to provide sane defaults for Data::Printer, so you'll never
257 have to worry about anything other than typing "p( $var )" in your
258 code. That said, and besides coloring and filtering, there are several
259 other customization options available, as shown below (with default
260 values):
261 use Data::Printer {
263 name => 'var', # name to display on cyclic references
264 indent => 4, # how many spaces in each indent
265 hash_separator => ' ', # what separates keys from values
266 align_hash => 1, # align values in hash
267 colored => 'auto', # colorize output (1 for always, 0 for never)
268 index => 1, # display array indices
269 multiline => 1, # display in multiple lines (see note below)
270 max_depth => 0, # how deep to traverse the data (0 for all)
271 sort_keys => 1, # sort hash keys
272 deparse => 0, # use B::Deparse to expand (expose) subroutines
273 show_tied => 1, # expose tied variables
274 show_tainted => 1, # expose tainted variables
275 show_unicode => 0, # show unicode flag if it exists
276 show_weak => 1, # expose weak references
277 show_readonly => 0, # expose scalar variables marked as read-only
278 show_lvalue => 1, # expose lvalue types
279 print_escapes => 0, # print non-printable chars as "\n", "\t", etc.
280 escape_chars => 'none', # escape chars into \x{...} form. Values are
281 # "none", "nonascii", "nonlatin1", "all"
282 quote_keys => 'auto', # quote hash keys (1 for always, 0 for never).
283 # 'auto' will quote when key is empty/space-only.
284 scalar_quotes => '"', # the quote symbols to enclose scalar values
285 separator => ',', # uses ',' to separate array/hash elements
286 end_separator => 0, # prints the separator after last element in array/hash.
287 # the default is 0 that means not to print
288 caller_info => 0, # include information on what's being printed
290 use_prototypes => 1, # allow p(%foo), but prevent anonymous data
291 return_value => 'dump', # what should p() return? See 'Return Value' above.
292 output => 'stderr',# where to print the output. See
293 # 'Changing output targets' above.
294 class_method => '_data_printer', # make classes aware of Data::Printer
296 # and able to dump themselves.
297 class => {
299 internals => 1, # show internal data structures of classes
300 inherited => 'none', # show inherited methods,
302 # can also be 'all', 'private', or 'public'.
303 universal => 1, # include UNIVERSAL methods in inheritance list
305 parents => 1, # show parents, if there are any
307 linear_isa => 'auto', # show the entire @ISA, linearized, whenever
308 # the object has more than one parent. Can
309 # also be set to 1 (always show) or 0 (never).
310 expand => 1, # how deep to traverse the object (in case
312 # it contains other objects). Defaults to
313 # 1, meaning expand only itself. Can be any
314 # number, 0 for no class expansion, and 'all'
315 # to expand everything.
316 sort_methods => 1, # sort public and private methods
318 show_methods => 'all' # method list. Also 'none', 'public', 'private'
320 },
321 };
322 Note: setting "multiline" to 0 will also set "index" and "indent" to 0.
324
326 Data::Printer offers you the ability to use filters to override any
327 kind of data display. The filters are placed on a hash, where keys are
328 the types - or class names - and values are anonymous subs that receive
329 two arguments: the item itself as first parameter, and the properties
330 hashref (in case your filter wants to read from it). This lets you
331 quickly override the way Data::Printer handles and displays data types
332 and, in particular, objects.
333 use Data::Printer filters => {
335 'DateTime' => sub { $_[0]->ymd },
336 'HTTP::Request' => sub { $_[0]->uri },
337 };
338 Perl types are named as "ref" calls them: SCALAR, ARRAY, HASH, REF,
340 CODE, Regexp and GLOB. As for objects, just use the class' name, as
341 shown above.
342 As of version 0.13, you may also use the '-class' filter, which will be
344 called for all non-perl types (objects).
345 Your filters are supposed to return a defined value (usually, the
347 string you want to print). If you don't, Data::Printer will let the
348 next filter of that same type have a go, or just fallback to the
349 defaults. You can also use an array reference to pass more than one
350 filter for the same type or class.
351 Note: If you plan on calling "p()" from within an inline filter, please
353 make sure you are passing only REFERENCES as arguments. See "CAVEATS"
354 below.
355 You may also like to specify standalone filter modules. Please see
357 Data::Printer::Filter for further information on a more powerful filter
358 interface for Data::Printer, including useful filters that are shipped
359 as part of this distribution.
360
362 Whenever printing the contents of a class, Data::Printer first checks
363 to see if that class implements a sub called '_data_printer' (or
364 whatever you set the "class_method" option to in your settings, see
365 "CUSTOMIZATION" below).
366 If a sub with that exact name is available in the target object,
368 Data::Printer will use it to get the string to print instead of making
369 a regular class dump.
370 This means you could have the following in one of your classes:
372 sub _data_printer {
374 my ($self, $properties) = @_;
375 return 'Hey, no peeking! But foo contains ' . $self->foo;
376 }
377 Notice you don't have to depend on Data::Printer at all, just write
379 your sub and it will use that to pretty-print your objects.
380 If you want to use colors and filter helpers, and still not add
382 Data::Printer to your dependencies, remember you can import them during
383 runtime:
384 sub _data_printer {
386 require Data::Printer::Filter;
387 Data::Printer::Filter->import;
388 # now we have 'indent', outdent', 'linebreak', 'p' and 'colored'
390 my ($self, $properties) = @_;
391 ...
392 }
393 Having a filter for that particular class will of course override this
395 setting.
396
398 Data::Printer tries to let you easily customize as much as possible
399 regarding the visualization of your data structures and objects. But
400 we don't want you to keep repeating yourself every time you want to use
401 it!
402 To avoid this, you can simply create a file called ".dataprinter" in
404 your home directory (usually "/home/username" in Linux), and put your
405 configuration hash reference in there.
406 This way, instead of doing something like:
408 use Data::Printer {
410 colour => {
411 array => 'bright_blue',
412 },
413 filters => {
414 'Catalyst::Request' => sub {
415 my $req = shift;
416 return "Cookies: " . p($req->cookies)
417 },
418 },
419 };
420 You can create a .dataprinter file that looks like this:
422 {
424 colour => {
425 array => 'bright_blue',
426 },
427 filters => {
428 'Catalyst::Request' => sub {
429 my $req = shift;
430 return "Cookies: " . p($req->cookies)
431 },
432 },
433 };
434 Note that all we did was remove the "use Data::Printer" bit when
436 writing the ".dataprinter" file. From then on all you have to do while
437 debugging scripts is:
438 use Data::Printer;
440 and it will load your custom settings every time :)
442 Loading RC files in custom locations
444 If your RC file is somewhere other than ".dataprinter" in your home
445 dir, you can load whichever file you want via the 'rc_file' parameter:
446 use Data::Printer rc_file => '/path/to/my/rcfile.conf';
448 You can even set this to undef or to a non-existing file to disable
450 your RC file at will.
451 The RC file location can also be specified with the "DATAPRINTERRC"
453 environment variable. Using "rc_file" in code will override the
454 environment variable.
455 RC File Security
457 The ".dataprinter" RC file is nothing but a Perl hash that gets
458 "eval"'d back into the code. This means that whatever is in your RC
459 file WILL BE INTERPRETED BY PERL AT RUNTIME. This can be quite
460 worrying if you're not the one in control of the RC file.
461 For this reason, Data::Printer takes extra precaution before loading
463 the file:
464 · The file has to be in your home directory unless you specifically
466 point elsewhere via the '"rc_file"' property or the DATAPRINTERRC
467 environment variable;
468 · The file must be a plain file, never a symbolic link, named pipe or
470 socket;
471 · The file must be owned by you (i.e. the effective user id that ran
473 the script using Data::Printer);
474 · The file must be read-only for everyone but your user. This
476 usually means permissions 0644, 0640 or 0600 in Unix-like systems.
477 THIS IS NOT CHECKED IN WIN32;
478 · The file will NOT be loaded in Taint mode, unless you specifically
480 load Data::Printer with the 'allow_tainted' option set to true. And
481 even if you do that, Data::Printer will still issue a warning
482 before loading the file. But seriously, don't do that.
483 Failure to comply with the security rules above will result in the RC
485 file not being loaded (likely with a warning on what went wrong).
486
488 You're likely to add/remove Data::Printer from source code being
489 developed and debugged all the time, and typing it might feel too long.
490 Because of this, the 'DDP' package is provided as a shorter alias to
491 Data::Printer:
492 use DDP;
494 p %some_var;
495
497 If you set caller_info to a true value, Data::Printer will prepend
498 every call with an informational message. For example:
499 use Data::Printer caller_info => 1;
501 my $var = 42;
503 p $var;
504 will output something like:
506 Printing in line 4 of myapp.pl:
508 42
509 The default message is 'Printing in line __LINE__ of __FILENAME__:'.
511 The special strings "__LINE__", "__FILENAME__" and "__PACKAGE__" will
512 be interpolated into their according value so you can customize them at
513 will:
514 use Data::Printer
516 caller_info => 1,
517 caller_message => "Okay, __PACKAGE__, let's dance!"
518 color => {
519 caller_info => 'bright_red',
520 };
521 As shown above, you may also set a color for "caller_info" in your
523 color hash. Default is cyan.
524
526 The following are volatile parts of the API which are subject to change
527 at any given version. Use them at your own risk.
528 Local Configuration (experimental!)
530 You can override global configurations by writing them as the second
531 parameter for p(). For example:
532 p( %var, color => { hash => 'green' } );
534 Filter classes
536 As of Data::Printer 0.11, you can create complex filters as a separate
537 module. Those can even be uploaded to CPAN and used by other people!
538 See Data::Printer::Filter for further information.
539
541 You can't pass more than one variable at a time.
542 p($foo, $bar); # wrong
544 p($foo); # right
545 p($bar); # right
546 You can't use it in variable declarations (it will most likely not do
548 what you want):
549 p my @array = qw(a b c d); # wrong
551 my @array = qw(a b c d); p @array; # right
552 The default mode is to use prototypes, in which you are supposed to
554 pass variables, not anonymous structures:
555 p( { foo => 'bar' } ); # wrong
557 p %somehash; # right
559 p $hash_ref; # also right
560 To pass anonymous structures, set "use_prototypes" option to 0. But
562 remember you'll have to pass your variables as references:
563 use Data::Printer use_prototypes => 0;
565 p( { foo => 'bar' } ); # was wrong, now is right.
567 p( %foo ); # was right, but fails without prototypes
569 p( \%foo ); # do this instead
570 If you are using inline filters, and calling p() (or whatever name you
572 aliased it to) from inside those filters, you must pass the arguments
573 to "p()" as a reference:
574 use Data::Printer {
576 filters => {
577 ARRAY => sub {
578 my $listref = shift;
579 my $string = '';
580 foreach my $item (@$listref) {
581 $string .= p( \$item ); # p( $item ) will not work!
582 }
583 return $string;
584 },
585 },
586 };
587 This happens because your filter function is compiled before
589 Data::Printer itself loads, so the filter does not see the function
590 prototype. As a way to avoid unpleasant surprises, if you forget to
591 pass a reference, Data::Printer will generate an exception for you with
592 the following message:
593 'When calling p() without prototypes, please pass arguments as references'
595 Another way to avoid this is to use the much more complete
597 Data::Printer::Filter interface for standalone filters.
598
600 Circumventing prototypes
601 The "p()" function uses prototypes by default, allowing you to say:
602 p %var;
604 instead of always having to pass references, like:
606 p \%var;
608 There are cases, however, where you may want to pass anonymous
610 structures, like:
611 p { foo => $bar }; # this blows up, don't use
613 and because of prototypes, you can't. If this is your case, just set
615 "use_prototypes" option to 0. Note, with this option, you will have to
616 pass your variables as references:
617 use Data::Printer use_prototypes => 0;
619 p { foo => 'bar' }; # doesn't blow up anymore, works just fine.
621 p %var; # but now this blows up...
623 p \%var; # ...so do this instead
624 p [ $foo, $bar, \@baz ]; # this way you can even pass
626 # several variables at once
627 Versions prior to 0.17 don't have the "use_prototypes" option. If
629 you're stuck in an older version you can write "&p()" instead of "p()"
630 to circumvent prototypes and pass elements (including anonymous
631 variables) as REFERENCES. This notation, however, requires enclosing
632 parentheses:
633 &p( { foo => $bar } ); # this is ok, use at will
635 &p( \"DEBUGGING THIS BIT" ); # this works too
636 Or you could just create a very simple wrapper function:
638 sub pp { p @_ };
640 And use it just as you use "p()".
642 Minding the return value of p()
644 (contributed by Matt S. Trout (mst))
645 There is a reason why explicit return statements are recommended unless
647 you know what you're doing. By default, Data::Printer's return value
648 depends on how it was called. When not in void context, it returns the
649 serialized form of the dump.
650 It's tempting to trust your own p() calls with that approach, but if
652 this is your last statement in a function, you should keep in mind your
653 debugging code will behave differently depending on how your function
654 was called!
655 To prevent that, set the "return_value" property to either 'void' or
657 'pass'. You won't be able to retrieve the dumped string but, hey, who
658 does that anyway :)
659 Assuming you have set the pass-through ('pass') property in your
661 ".dataprinter" file, another stunningly useful thing you can do with it
662 is change code that says:
663 return $obj->foo;
665 with:
667 use DDP;
669 return p $obj->foo;
671 You can even add it to chained calls if you wish to see the dump of a
673 particular state, changing this:
674 $obj->foo->bar->baz;
676 to:
678 $obj->foo->DDP::p->bar->baz
680 And things will "Just Work".
682 Using p() in some/all of your loaded modules
684 (contributed by Matt S. Trout (mst))
685 While debugging your software, you may want to use Data::Printer in
687 some or all loaded modules and not bother having to load it in each and
688 every one of them. To do this, in any module loaded by "myapp.pl",
689 simply write:
690 ::p( @myvar ); # note the '::' in front of p()
692 Then call your program like:
694 perl -MDDP myapp.pl
696 This also has the great advantage that if you leave one p() call in by
698 accident, it will fail without the -M, making it easier to spot :)
699 If you really want to have p() imported into your loaded modules, use
701 the next tip instead.
702 Adding p() to all your loaded modules
704 (contributed by Árpád Szász)
705 If you wish to automatically add Data::Printer's "p()" function to
707 every loaded module in you app, you can do something like this to your
708 main program:
709 BEGIN {
711 {
712 no strict 'refs';
713 require Data::Printer;
714 my $alias = 'p';
715 foreach my $package ( keys %main:: ) {
716 if ( $package =~ m/::$/ ) {
717 *{ $package . $alias } = \&Data::Printer::p;
718 }
719 }
720 }
721 }
722 WARNING This will override all locally defined subroutines/methods that
724 are named "p", if they exist, in every loaded module. If you already
725 have a subroutine named '"p()"', be sure to change $alias to something
726 custom.
727 If you rather avoid namespace manipulation altogether, use the previous
729 tip instead.
730 Using Data::Printer from the Perl debugger
732 (contributed by Árpád Szász and Marcel Grünauer (hanekomu))
733 With DB::Pluggable, you can easily set the perl debugger to use
735 Data::Printer to print variable information, replacing the debugger's
736 standard "p()" function. All you have to do is add these lines to your
737 ".perldb" file:
738 use DB::Pluggable;
740 DB::Pluggable->run_with_config( \'[DataPrinter]' ); # note the '\'
741 Then call the perl debugger as you normally would:
743 perl -d myapp.pl
745 Now Data::Printer's "p()" command will be used instead of the
747 debugger's!
748 See perldebug for more information on how to use the perl debugger, and
750 DB::Pluggable for extra functionality and other plugins.
751 If you can't or don't wish to use DB::Pluggable, or simply want to keep
753 the debugger's "p()" function and add an extended version using
754 Data::Printer (let's call it "px()" for instance), you can add these
755 lines to your ".perldb" file instead:
756 $DB::alias{px} = 's/px/DB::px/';
758 sub px {
759 my $expr = shift;
760 require Data::Printer;
761 print Data::Printer::p($expr);
762 }
763 Now, inside the Perl debugger, you can pass as reference to "px"
765 expressions to be dumped using Data::Printer.
766 Using Data::Printer in a perl shell (REPL)
768 Some people really enjoy using a REPL shell to quickly try Perl code.
769 One of the most famous ones out there is Devel::REPL. If you use it,
770 now you can also see its output with Data::Printer!
771 Just install Devel::REPL::Plugin::DataPrinter and add the following
773 line to your re.pl configuration file (usually ".re.pl/repl.rc" in your
774 home dir):
775 load_plugin('DataPrinter');
777 The next time you run "re.pl", it should dump all your REPL using
779 Data::Printer!
780 Easily rendering Data::Printer's output as HTML
782 To turn Data::Printer's output into HTML, you can do something like:
783 use HTML::FromANSI;
785 use Data::Printer;
786 my $html_output = ansi2html( p($object, colored => 1) );
788 In the example above, the $html_output variable contains the HTML
790 escaped output of "p($object)", so you can print it for later
791 inspection or render it (if it's a web app).
792 Using Data::Printer with Template Toolkit
794 (contributed by Stephen Thirlwall (sdt))
795 If you use Template Toolkit and want to dump your variables using
797 Data::Printer, install the Template::Plugin::DataPrinter module and
798 load it in your template:
799 [% USE DataPrinter %]
801 The provided methods match those of "Template::Plugin::Dumper":
803 ansi-colored dump of the data structure in "myvar":
805 [% DataPrinter.dump( myvar ) %]
806 html-formatted, colored dump of the same data structure:
808 [% DataPrinter.dump_html( myvar ) %]
809 The module allows several customization options, even letting you load
811 it as a complete drop-in replacement for Template::Plugin::Dumper so
812 you don't even have to change your previous templates!
813 Unified interface for Data::Printer and other debug formatters
815 (contributed by Kevin McGrath (catlgrep))
816 If you are porting your code to use Data::Printer instead of
818 Data::Dumper or similar, you can just replace:
819 use Data::Dumper;
821 with:
823 use Data::Printer alias => 'Dumper';
825 # use Data::Dumper;
826 making sure to provide Data::Printer with the proper alias for the
828 previous dumping function.
829 If, however, you want a really unified approach where you can easily
831 flip between debugging outputs, use Any::Renderer and its plugins, like
832 Any::Renderer::Data::Printer.
833 Printing stack traces with arguments expanded using Data::Printer
835 (contributed by Sergey Aleynikov (randir))
836 There are times where viewing the current state of a variable is not
838 enough, and you want/need to see a full stack trace of a function call.
839 The Devel::PrettyTrace module uses Data::Printer to provide you just
841 that. It exports a "bt()" function that pretty-prints detailed
842 information on each function in your stack, making it easier to spot
843 any issues!
844 Troubleshooting apps in real time without changing a single line of your
846 code
847 (contributed by Marcel Grünauer (hanekomu))
848 dip is a dynamic instrumentation framework for troubleshooting Perl
850 programs, similar to DTrace
851 <http://opensolaris.org/os/community/dtrace/>. In a nutshell, "dip"
852 lets you create probes for certain conditions in your application that,
853 once met, will perform a specific action. Since it uses Aspect-oriented
854 programming, it's very lightweight and you only pay for what you use.
855 "dip" can be very useful since it allows you to debug your software
857 without changing a single line of your original code. And Data::Printer
858 comes bundled with it, so you can use the "p()" function to view your
859 data structures too!
860 # Print a stack trace every time the name is changed,
862 # except when reading from the database.
863 dip -e 'before { print longmess(p $_->{args}[1]) if $_->{args}[1] }
864 call "MyObj::name" & !cflow("MyObj::read")' myapp.pl
865 You can check you dip's own documentation for more information and
867 options.
868 Sample output for color fine-tuning
870 (contributed by Yanick Champoux (yanick))
871 The "examples/try_me.pl" file included in this distribution has a
873 sample dump with a complex data structure to let you quickly test color
874 schemes.
875 creating fiddling filters
877 (contributed by dirk)
878 Sometimes, you may want to take advantage of Data::Printer's original
880 dump, but add/change some of the original data to enhance your
881 debugging ability. Say, for example, you have an "HTTP::Response"
882 object you want to print but the content is encoded. The basic
883 approach, of course, would be to just dump the decoded content:
884 use DDP filter {
886 'HTTP::Response' => sub { p( \shift->decoded_content, %{shift} );
887 };
888 But what if you want to see the rest of the original object? Dumping it
890 would be a no-go, because you would just recurse forever in your own
891 filter.
892 Never fear! When you create a filter in Data::Printer, you're not
894 replacing the original one, you're just stacking yours on top of it. To
895 forward your data to the original filter, all you have to do is return
896 an undefined value. This means you can rewrite your "HTTP::Response"
897 filter like so, if you want:
898 use DDP filters => {
900 'HTTP::Response' => sub {
901 my ($res, $p) = @_;
902 # been here before? Switch to original handler
904 return if exists $res->{decoded_content};
905 # first timer? Come on in!
907 my $clone = $res->clone;
908 $clone->{decoded_content} = $clone->decoded_content;
909 return p($clone, %$p);
910 }
911 };
912 And voilà! Your fiddling filter now works like a charm :)
914
916 If you find any, please file a bug report.
917
919 Data::Dumper
920 Data::Dump
922 Data::Dumper::Concise
924 Data::Dump::Streamer
926 Data::PrettyPrintObjects
928 Data::TreeDumper
930
932 Breno G. de Oliveira "<garu at cpan.org>"
933
935 Many thanks to everyone that helped design and develop this module with
936 patches, bug reports, wishlists, comments and tests. They are
937 (alphabetically):
938 · Adam Rosenstein
940 · Allan Whiteford
942 · Andreas König
944 · Andy Bach
946 · Árpád Szász
948 · Athanasios Douitsis (aduitsis)
950 · Baldur Kristinsson
952 · brian d foy
954 · Chad Granum (exodist)
956 · Chris Prather (perigrin)
958 · Dave Mitchell
960 · David D Lowe (Flimm)
962 · David Golden (xdg)
964 · David Precious (bigpresh)
966 · David Raab
968 · Damien Krotkine (dams)
970 · Denis Howe
972 · Dotan Dimet
974 · Eden Cardim (edenc)
976 · Elliot Shank (elliotjs)
978 · Fernando Corrêa (SmokeMachine)
980 · Fitz Elliott
982 · Frew Schmidt (frew)
984 · Ivan Bessarabov (bessarabv)
986 · J Mash
988 · Jay Allen (jayallen)
990 · Jesse Luehrs (doy)
992 · Jim Keenan (jkeenan)
994 · Joel Berger (jberger)
996 · John S. Anderson (genehack)
998 · Kartik Thakore (kthakore)
1000 · Kevin Dawson (bowtie)
1002 · Kevin McGrath (catlgrep)
1004 · Kip Hampton (ubu)
1006 · Marcel Grünauer (hanekomu)
1008 · Marco Masetti (grubert65)
1010 · Mark Fowler (Trelane)
1012 · Matt S. Trout (mst)
1014 · Maxim Vuets
1016 · Michael Conrad
1018 · Mike Doherty (doherty)
1020 · Nuba Princigalli (nuba)
1022 · Olaf Alders (oalders)
1024 · Paul Evans (LeoNerd)
1026 · Pedro Melo (melo)
1028 · Przemysław Wesołek (jest)
1030 · Rebecca Turner (iarna)
1032 · Renato Cron (renatoCRON)
1034 · Ricardo Signes (rjbs)
1036 · Rob Hoelz (hoelzro)
1038 · sawyer
1040 · Sebastian Willing (Sewi)
1042 · Sergey Aleynikov (randir)
1044 · Stanislaw Pusep (syp)
1046 · Stephen Thirlwall (sdt)
1048 · sugyan
1050 · Tatsuhiko Miyagawa (miyagawa)
1052 · Thomas Sibley (tsibley)
1054 · Tim Heaney (oylenshpeegul)
1056 · Torsten Raudssus (Getty)
1058 · Tokuhiro Matsuno (tokuhirom)
1060 · vividsnow
1062 · Wesley Dal`Col (blabos)
1064 · Yanick Champoux (yanick)
1066 · Zefram
1068 If I missed your name, please drop me a line!
1070
1072 Copyright 2011-2017 Breno G. de Oliveira "<garu at cpan.org>". All
1073 rights reserved.
1074 This module is free software; you can redistribute it and/or modify it
1076 under the same terms as Perl itself. See perlartistic.
1077
1079 BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
1080 FOR THE SOFTWARE, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT
1081 WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER
1082 PARTIES PROVIDE THE SOFTWARE "AS IS" WITHOUT WARRANTY OF ANY KIND,
1083 EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
1084 WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE
1085 ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE SOFTWARE IS WITH
1086 YOU. SHOULD THE SOFTWARE PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL
1087 NECESSARY SERVICING, REPAIR, OR CORRECTION.
1088 IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
1090 WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
1091 REDISTRIBUTE THE SOFTWARE AS PERMITTED BY THE ABOVE LICENCE, BE LIABLE
1092 TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL, OR
1093 CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE
1094 SOFTWARE (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING
1095 RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A
1096 FAILURE OF THE SOFTWARE TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF
1097 SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
1098 DAMAGES.
1099perl v5.30.1 2020-01-29 Data::Printer(3)