4 # convert perl data structures into perl syntax suitable for both printing
7 # Documentation at the __END__
12 $VERSION = $VERSION = '2.101';
23 @ISA = qw(Exporter DynaLoader);
25 @EXPORT_OK = qw(DumperX);
27 bootstrap Data::Dumper;
29 # module vars and their defaults
30 $Indent = 2 unless defined $Indent;
31 $Purity = 0 unless defined $Purity;
32 $Pad = "" unless defined $Pad;
33 $Varname = "VAR" unless defined $Varname;
34 $Useqq = 0 unless defined $Useqq;
35 $Terse = 0 unless defined $Terse;
36 $Freezer = "" unless defined $Freezer;
37 $Toaster = "" unless defined $Toaster;
38 $Deepcopy = 0 unless defined $Deepcopy;
39 $Quotekeys = 1 unless defined $Quotekeys;
40 $Bless = "bless" unless defined $Bless;
41 #$Expdepth = 0 unless defined $Expdepth;
42 #$Maxdepth = 0 unless defined $Maxdepth;
45 # expects an arrayref of values to be dumped.
46 # can optionally pass an arrayref of names for the values.
47 # names must have leading $ sign stripped. begin the name with *
48 # to cause output of arrays and hashes rather than refs.
53 croak "Usage: PACKAGE->new(ARRAYREF, [ARRAYREF])"
54 unless (defined($v) && (ref($v) eq 'ARRAY'));
55 $n = [] unless (defined($n) && (ref($v) eq 'ARRAY'));
58 level => 0, # current recursive depth
59 indent => $Indent, # various styles of indenting
60 pad => $Pad, # all lines prefixed by this string
61 xpad => "", # padding-per-level
62 apad => "", # added padding for hash keys n such
63 sep => "", # list separator
64 seen => {}, # local (nested) refs (id => [name, val])
65 todump => $v, # values to dump []
66 names => $n, # optional names for values []
67 varname => $Varname, # prefix to use for tagging nameless ones
68 purity => $Purity, # degree to which output is evalable
69 useqq => $Useqq, # use "" for strings (backslashitis ensues)
70 terse => $Terse, # avoid name output (where feasible)
71 freezer => $Freezer, # name of Freezer method for objects
72 toaster => $Toaster, # name of method to revive objects
73 deepcopy => $Deepcopy, # dont cross-ref, except to stop recursion
74 quotekeys => $Quotekeys, # quote hash keys
75 'bless' => $Bless, # keyword to use for "bless"
76 # expdepth => $Expdepth, # cutoff depth for explicit dumping
77 # maxdepth => $Maxdepth, # depth beyond which we give up
88 # add-to or query the table of already seen references
92 if (defined($g) && (ref($g) eq 'HASH')) {
94 while (($k, $v) = each %$g) {
95 if (defined $v and ref $v) {
96 ($id) = (overload::StrVal($v) =~ /\((.*)\)$/);
97 if ($k =~ /^[*](.*)$/) {
98 $k = (ref $v eq 'ARRAY') ? ( "\\\@" . $1 ) :
99 (ref $v eq 'HASH') ? ( "\\\%" . $1 ) :
100 (ref $v eq 'CODE') ? ( "\\\&" . $1 ) :
103 elsif ($k !~ /^\$/) {
106 $s->{seen}{$id} = [$k, $v];
109 carp "Only refs supported, ignoring non-ref item \$$k";
115 return map { @$_ } values %{$s->{seen}};
120 # set or query the values to be dumped
124 if (defined($v) && (ref($v) eq 'ARRAY')) {
125 $s->{todump} = [@$v]; # make a copy
129 return @{$s->{todump}};
134 # set or query the names of the values to be dumped
138 if (defined($n) && (ref($n) eq 'ARRAY')) {
139 $s->{names} = [@$n]; # make a copy
143 return @{$s->{names}};
150 # dump the refs in the current dumper object.
151 # expects same args as new() if called via package name.
155 my(@out, $val, $name);
159 $s = $s->new(@_) unless ref $s;
161 for $val (@{$s->{todump}}) {
164 $name = $s->{names}[$i++];
166 if ($name =~ /^[*](.*)$/) {
168 $name = (ref $val eq 'ARRAY') ? ( "\@" . $1 ) :
169 (ref $val eq 'HASH') ? ( "\%" . $1 ) :
170 (ref $val eq 'CODE') ? ( "\*" . $1 ) :
177 elsif ($name !~ /^\$/) {
178 $name = "\$" . $name;
182 $name = "\$" . $s->{varname} . $i;
187 local($s->{apad}) = $s->{apad};
188 $s->{apad} .= ' ' x (length($name) + 3) if $s->{indent} >= 2;
189 $valstr = $s->_dump($val, $name);
192 $valstr = "$name = " . $valstr . ';' if @post or !$s->{terse};
193 $out .= $s->{pad} . $valstr . $s->{sep};
194 $out .= $s->{pad} . join(';' . $s->{sep} . $s->{pad}, @post)
195 . ';' . $s->{sep} if @post;
199 return wantarray ? @out : join('', @out);
203 # twist, toil and turn;
204 # and recurse, of course.
207 my($s, $val, $name) = @_;
209 my($out, $realpack, $realtype, $type, $ipad, $id, $blesspad);
216 # prep it, if it looks like an object
217 if ($type =~ /[a-z_:]/) {
218 my $freezer = $s->{freezer};
219 $val->$freezer() if $freezer && UNIVERSAL::can($val, $freezer);
222 ($realpack, $realtype, $id) =
223 (overload::StrVal($val) =~ /^(?:(.*)\=)?([^=]*)\(([^\(]*)\)$/);
225 # if it has a name, we need to either look it up, or keep a tab
226 # on it so we know when we hit it later
227 if (defined($name) and length($name)) {
228 # keep a tab on it so that we dont fall into recursive pit
229 if (exists $s->{seen}{$id}) {
230 # if ($s->{expdepth} < $s->{level}) {
231 if ($s->{purity} and $s->{level} > 0) {
232 $out = ($realtype eq 'HASH') ? '{}' :
233 ($realtype eq 'ARRAY') ? '[]' :
235 push @post, $name . " = " . $s->{seen}{$id}[0];
238 $out = $s->{seen}{$id}[0];
239 if ($name =~ /^([\@\%])/) {
241 if ($out =~ /^\\$start/) {
242 $out = substr($out, 1);
245 $out = $start . '{' . $out . '}';
254 $s->{seen}{$id} = [ (($name =~ /^[@%]/) ? ('\\' . $name ) :
255 ($realtype eq 'CODE' and
256 $name =~ /^[*](.*)$/) ? ('\\&' . $1 ) :
263 if ($realpack eq 'Regexp') {
268 else { # we have a blessed ref
269 $out = $s->{'bless'} . '( ';
270 $blesspad = $s->{apad};
271 $s->{apad} .= ' ' if ($s->{indent} >= 2);
276 $ipad = $s->{xpad} x $s->{level};
279 if ($realtype eq 'SCALAR') {
281 $out .= 'do{\\(my $o = ' . $s->_dump($$val, "\${$name}") . ')}';
284 $out .= '\\' . $s->_dump($$val, "\${$name}");
287 elsif ($realtype eq 'GLOB') {
288 $out .= '\\' . $s->_dump($$val, "*{$name}");
290 elsif ($realtype eq 'ARRAY') {
291 my($v, $pad, $mname);
293 $out .= ($name =~ /^\@/) ? '(' : '[';
294 $pad = $s->{sep} . $s->{pad} . $s->{apad};
295 ($name =~ /^\@(.*)$/) ? ($mname = "\$" . $1) :
296 # omit -> if $foo->[0]->{bar}, but not ${$foo->[0]}->{bar}
297 ($name =~ /^\\?[\%\@\*\$][^{].*[]}]$/) ? ($mname = $name) :
298 ($mname = $name . '->');
299 $mname .= '->' if $mname =~ /^\*.+\{[A-Z]+\}$/;
301 $sname = $mname . '[' . $i . ']';
302 $out .= $pad . $ipad . '#' . $i if $s->{indent} >= 3;
303 $out .= $pad . $ipad . $s->_dump($v, $sname);
304 $out .= "," if $i++ < $#$val;
306 $out .= $pad . ($s->{xpad} x ($s->{level} - 1)) if $i;
307 $out .= ($name =~ /^\@/) ? ')' : ']';
309 elsif ($realtype eq 'HASH') {
310 my($k, $v, $pad, $lpad, $mname);
311 $out .= ($name =~ /^\%/) ? '(' : '{';
312 $pad = $s->{sep} . $s->{pad} . $s->{apad};
314 ($name =~ /^\%(.*)$/) ? ($mname = "\$" . $1) :
315 # omit -> if $foo->[0]->{bar}, but not ${$foo->[0]}->{bar}
316 ($name =~ /^\\?[\%\@\*\$][^{].*[]}]$/) ? ($mname = $name) :
317 ($mname = $name . '->');
318 $mname .= '->' if $mname =~ /^\*.+\{[A-Z]+\}$/;
319 while (($k, $v) = each %$val) {
320 my $nk = $s->_dump($k, "");
321 $nk = $1 if !$s->{quotekeys} and $nk =~ /^[\"\']([A-Za-z_]\w*)[\"\']$/;
322 $sname = $mname . '{' . $nk . '}';
323 $out .= $pad . $ipad . $nk . " => ";
325 # temporarily alter apad
326 $s->{apad} .= (" " x (length($nk) + 4)) if $s->{indent} >= 2;
327 $out .= $s->_dump($val->{$k}, $sname) . ",";
328 $s->{apad} = $lpad if $s->{indent} >= 2;
330 if (substr($out, -1) eq ',') {
332 $out .= $pad . ($s->{xpad} x ($s->{level} - 1));
334 $out .= ($name =~ /^\%/) ? ')' : '}';
336 elsif ($realtype eq 'CODE') {
337 $out .= 'sub { "DUMMY" }';
338 carp "Encountered CODE ref, using dummy placeholder" if $s->{purity};
341 croak "Can\'t handle $realtype type.";
344 if ($realpack) { # we have a blessed ref
345 $out .= ', \'' . $realpack . '\'' . ' )';
346 $out .= '->' . $s->{toaster} . '()' if $s->{toaster} ne '';
347 $s->{apad} = $blesspad;
352 else { # simple scalar
355 # first, catalog the scalar
357 ($id) = ("$ref" =~ /\(([^\(]*)\)$/);
358 if (exists $s->{seen}{$id}) {
359 if ($s->{seen}{$id}[2]) {
360 $out = $s->{seen}{$id}[0];
366 #warn "[>\\$name]\n";
367 $s->{seen}{$id} = ["\\$name", $ref];
370 if (ref($ref) eq 'GLOB' or "$ref" =~ /=GLOB\([^()]+\)$/) { # glob
371 my $name = substr($val, 1);
372 if ($name =~ /^[A-Za-z_][\w:]*$/) {
373 $name =~ s/^main::/::/;
377 $sname = $s->_dump($name, "");
378 $sname = '{' . $sname . '}';
382 local ($s->{level}) = 0;
383 for $k (qw(SCALAR ARRAY HASH)) {
384 my $gval = *$val{$k};
385 next unless defined $gval;
386 next if $k eq "SCALAR" && ! defined $$gval; # always there
388 # _dump can push into @post, so we hold our place using $postlen
389 my $postlen = scalar @post;
390 $post[$postlen] = "\*$sname = ";
391 local ($s->{apad}) = " " x length($post[$postlen]) if $s->{indent} >= 2;
392 $post[$postlen] .= $s->_dump($gval, "\*$sname\{$k\}");
395 $out .= '*' . $sname;
397 elsif (!defined($val)) {
400 elsif ($val =~ /^(?:0|-?[1-9]\d{0,8})$/) { # safe decimal number
405 $out .= qquote($val, $s->{useqq});
408 $val =~ s/([\\\'])/\\$1/g;
409 $out .= '\'' . $val . '\'';
414 # if we made it this far, $id was added to seen list at current
415 # level, so remove it to get deep copies
416 if ($s->{deepcopy}) {
417 delete($s->{seen}{$id});
420 $s->{seen}{$id}[2] = 1;
427 # non-OO style of earlier version
430 return Data::Dumper->Dump([@_]);
434 # same, only calls the XS version
437 return Data::Dumper->Dumpxs([@_], []);
440 sub Dumpf { return Data::Dumper->Dump(@_) }
442 sub Dumpp { print Data::Dumper->Dump(@_) }
445 # reset the "seen" cache
474 defined($v) ? (($s->{pad} = $v), return $s) : $s->{pad};
479 defined($v) ? (($s->{varname} = $v), return $s) : $s->{varname};
484 defined($v) ? (($s->{purity} = $v), return $s) : $s->{purity};
489 defined($v) ? (($s->{useqq} = $v), return $s) : $s->{useqq};
494 defined($v) ? (($s->{terse} = $v), return $s) : $s->{terse};
499 defined($v) ? (($s->{freezer} = $v), return $s) : $s->{freezer};
504 defined($v) ? (($s->{toaster} = $v), return $s) : $s->{toaster};
509 defined($v) ? (($s->{deepcopy} = $v), return $s) : $s->{deepcopy};
514 defined($v) ? (($s->{quotekeys} = $v), return $s) : $s->{quotekeys};
519 defined($v) ? (($s->{'bless'} = $v), return $s) : $s->{'bless'};
522 # used by qquote below
533 # put a string value in double quotes
536 s/([\\\"\@\$])/\\$1/g;
537 return qq("$_") unless /[^\040-\176]/; # fast exit
539 my $high = shift || "";
540 s/([\a\b\t\n\f\r\e])/$esc{$1}/g;
542 # no need for 3 digits in escape for these
543 s/([\0-\037])(?!\d)/'\\'.sprintf('%o',ord($1))/eg;
545 s/([\0-\037\177])/'\\'.sprintf('%03o',ord($1))/eg;
546 if ($high eq "iso8859") {
547 s/([\200-\240])/'\\'.sprintf('%o',ord($1))/eg;
548 } elsif ($high eq "utf8") {
550 # $str =~ s/([^\040-\176])/sprintf "\\x{%04x}", ord($1)/ge;
551 } elsif ($high eq "8bit") {
554 s/([\0-\037\177-\377])/'\\'.sprintf('%03o',ord($1))/eg;
564 Data::Dumper - stringified perl data structures, suitable for both printing and C<eval>
571 # simple procedural interface
572 print Dumper($foo, $bar);
574 # extended usage with names
575 print Data::Dumper->Dump([$foo, $bar], [qw(foo *ary)]);
577 # configuration variables
579 local $Data::Dump::Purity = 1;
580 eval Data::Dumper->Dump([$foo, $bar], [qw(foo *ary)]);
584 $d = Data::Dumper->new([$foo, $bar], [qw(foo *ary)]);
588 $d->Purity(1)->Terse(1)->Deepcopy(1);
594 Given a list of scalars or reference variables, writes out their contents in
595 perl syntax. The references can also be objects. The contents of each
596 variable is output in a single Perl statement. Handles self-referential
597 structures correctly.
599 The return value can be C<eval>ed to get back an identical copy of the
600 original reference structure.
602 Any references that are the same as one of those passed in will be named
603 C<$VAR>I<n> (where I<n> is a numeric suffix), and other duplicate references
604 to substructures within C<$VAR>I<n> will be appropriately labeled using arrow
605 notation. You can specify names for individual values to be dumped if you
606 use the C<Dump()> method, or you can change the default C<$VAR> prefix to
607 something else. See C<$Data::Dumper::Varname> and C<$Data::Dumper::Terse>
610 The default output of self-referential structures can be C<eval>ed, but the
611 nested references to C<$VAR>I<n> will be undefined, since a recursive
612 structure cannot be constructed using one Perl statement. You should set the
613 C<Purity> flag to 1 to get additional statements that will correctly fill in
616 In the extended usage form, the references to be dumped can be given
617 user-specified names. If a name begins with a C<*>, the output will
618 describe the dereferenced type of the supplied reference for hashes and
619 arrays, and coderefs. Output of names will be avoided where possible if
620 the C<Terse> flag is set.
622 In many cases, methods that are used to set the internal state of the
623 object will return the object itself, so method calls can be conveniently
626 Several styles of output are possible, all controlled by setting
627 the C<Indent> flag. See L<Configuration Variables or Methods> below
635 =item I<PACKAGE>->new(I<ARRAYREF [>, I<ARRAYREF]>)
637 Returns a newly created C<Data::Dumper> object. The first argument is an
638 anonymous array of values to be dumped. The optional second argument is an
639 anonymous array of names for the values. The names need not have a leading
640 C<$> sign, and must be comprised of alphanumeric characters. You can begin
641 a name with a C<*> to specify that the dereferenced type must be dumped
642 instead of the reference itself, for ARRAY and HASH references.
644 The prefix specified by C<$Data::Dumper::Varname> will be used with a
645 numeric suffix if the name for a value is undefined.
647 Data::Dumper will catalog all references encountered while dumping the
648 values. Cross-references (in the form of names of substructures in perl
649 syntax) will be inserted at all possible points, preserving any structural
650 interdependencies in the original set of values. Structure traversal is
651 depth-first, and proceeds in order from the first supplied value to
654 =item I<$OBJ>->Dump I<or> I<PACKAGE>->Dump(I<ARRAYREF [>, I<ARRAYREF]>)
656 Returns the stringified form of the values stored in the object (preserving
657 the order in which they were supplied to C<new>), subject to the
658 configuration options below. In an array context, it returns a list
659 of strings corresponding to the supplied values.
661 The second form, for convenience, simply calls the C<new> method on its
662 arguments before dumping the object immediately.
664 =item I<$OBJ>->Dumpxs I<or> I<PACKAGE>->Dumpxs(I<ARRAYREF [>, I<ARRAYREF]>)
666 This method is available if you were able to compile and install the XSUB
667 extension to C<Data::Dumper>. It is exactly identical to the C<Dump> method
668 above, only about 4 to 5 times faster, since it is written entirely in C.
670 =item I<$OBJ>->Seen(I<[HASHREF]>)
672 Queries or adds to the internal table of already encountered references.
673 You must use C<Reset> to explicitly clear the table if needed. Such
674 references are not dumped; instead, their names are inserted wherever they
675 are encountered subsequently. This is useful especially for properly
676 dumping subroutine references.
678 Expects a anonymous hash of name => value pairs. Same rules apply for names
679 as in C<new>. If no argument is supplied, will return the "seen" list of
680 name => value pairs, in an array context. Otherwise, returns the object
683 =item I<$OBJ>->Values(I<[ARRAYREF]>)
685 Queries or replaces the internal array of values that will be dumped.
686 When called without arguments, returns the values. Otherwise, returns the
689 =item I<$OBJ>->Names(I<[ARRAYREF]>)
691 Queries or replaces the internal array of user supplied names for the values
692 that will be dumped. When called without arguments, returns the names.
693 Otherwise, returns the object itself.
697 Clears the internal table of "seen" references and returns the object
706 =item Dumper(I<LIST>)
708 Returns the stringified form of the values in the list, subject to the
709 configuration options below. The values will be named C<$VAR>I<n> in the
710 output, where I<n> is a numeric suffix. Will return a list of strings
713 =item DumperX(I<LIST>)
715 Identical to the C<Dumper()> function above, but this calls the XSUB
716 implementation. Only available if you were able to compile and install
717 the XSUB extensions in C<Data::Dumper>.
721 =head2 Configuration Variables or Methods
723 Several configuration variables can be used to control the kind of output
724 generated when using the procedural interface. These variables are usually
725 C<local>ized in a block so that other parts of the code are not affected by
728 These variables determine the default state of the object created by calling
729 the C<new> method, but cannot be used to alter the state of the object
730 thereafter. The equivalent method names should be used instead to query
731 or set the internal state of the object.
733 The method forms return the object itself when called with arguments,
734 so that they can be chained together nicely.
738 =item $Data::Dumper::Indent I<or> I<$OBJ>->Indent(I<[NEWVAL]>)
740 Controls the style of indentation. It can be set to 0, 1, 2 or 3. Style 0
741 spews output without any newlines, indentation, or spaces between list
742 items. It is the most compact format possible that can still be called
743 valid perl. Style 1 outputs a readable form with newlines but no fancy
744 indentation (each level in the structure is simply indented by a fixed
745 amount of whitespace). Style 2 (the default) outputs a very readable form
746 which takes into account the length of hash keys (so the hash value lines
747 up). Style 3 is like style 2, but also annotates the elements of arrays
748 with their index (but the comment is on its own line, so array output
749 consumes twice the number of lines). Style 2 is the default.
751 =item $Data::Dumper::Purity I<or> I<$OBJ>->Purity(I<[NEWVAL]>)
753 Controls the degree to which the output can be C<eval>ed to recreate the
754 supplied reference structures. Setting it to 1 will output additional perl
755 statements that will correctly recreate nested references. The default is
758 =item $Data::Dumper::Pad I<or> I<$OBJ>->Pad(I<[NEWVAL]>)
760 Specifies the string that will be prefixed to every line of the output.
761 Empty string by default.
763 =item $Data::Dumper::Varname I<or> I<$OBJ>->Varname(I<[NEWVAL]>)
765 Contains the prefix to use for tagging variable names in the output. The
768 =item $Data::Dumper::Useqq I<or> I<$OBJ>->Useqq(I<[NEWVAL]>)
770 When set, enables the use of double quotes for representing string values.
771 Whitespace other than space will be represented as C<[\n\t\r]>, "unsafe"
772 characters will be backslashed, and unprintable characters will be output as
773 quoted octal integers. Since setting this variable imposes a performance
774 penalty, the default is 0. The C<Dumpxs()> method does not honor this
777 =item $Data::Dumper::Terse I<or> I<$OBJ>->Terse(I<[NEWVAL]>)
779 When set, Data::Dumper will emit single, non-self-referential values as
780 atoms/terms rather than statements. This means that the C<$VAR>I<n> names
781 will be avoided where possible, but be advised that such output may not
782 always be parseable by C<eval>.
784 =item $Data::Dumper::Freezer I<or> $I<OBJ>->Freezer(I<[NEWVAL]>)
786 Can be set to a method name, or to an empty string to disable the feature.
787 Data::Dumper will invoke that method via the object before attempting to
788 stringify it. This method can alter the contents of the object (if, for
789 instance, it contains data allocated from C), and even rebless it in a
790 different package. The client is responsible for making sure the specified
791 method can be called via the object, and that the object ends up containing
792 only perl data types after the method has been called. Defaults to an empty
795 =item $Data::Dumper::Toaster I<or> $I<OBJ>->Toaster(I<[NEWVAL]>)
797 Can be set to a method name, or to an empty string to disable the feature.
798 Data::Dumper will emit a method call for any objects that are to be dumped
799 using the syntax C<bless(DATA, CLASS)->METHOD()>. Note that this means that
800 the method specified will have to perform any modifications required on the
801 object (like creating new state within it, and/or reblessing it in a
802 different package) and then return it. The client is responsible for making
803 sure the method can be called via the object, and that it returns a valid
804 object. Defaults to an empty string.
806 =item $Data::Dumper::Deepcopy I<or> $I<OBJ>->Deepcopy(I<[NEWVAL]>)
808 Can be set to a boolean value to enable deep copies of structures.
809 Cross-referencing will then only be done when absolutely essential
810 (i.e., to break reference cycles). Default is 0.
812 =item $Data::Dumper::Quotekeys I<or> $I<OBJ>->Quotekeys(I<[NEWVAL]>)
814 Can be set to a boolean value to control whether hash keys are quoted.
815 A false value will avoid quoting hash keys when it looks like a simple
816 string. Default is 1, which will always enclose hash keys in quotes.
818 =item $Data::Dumper::Bless I<or> $I<OBJ>->Bless(I<[NEWVAL]>)
820 Can be set to a string that specifies an alternative to the C<bless>
821 builtin operator used to create objects. A function with the specified
822 name should exist, and should accept the same arguments as the builtin.
837 Run these code snippets to get a quick feel for the behavior of this
838 module. When you are through with these examples, you may want to
839 add or change the various configuration variables described above,
840 to see their behavior. (See the testsuite in the Data::Dumper
841 distribution for more examples.)
847 sub new {bless {'a' => 1, 'b' => sub { return "foo" }}, $_[0]};
849 package Fuz; # a weird REF-REF-SCALAR object
850 sub new {bless \($_ = \ 'fu\'z'), $_[0]};
855 $boo = [ 1, [], "abcd", \*foo,
856 {1 => 'a', 023 => 'b', 0x45 => 'c'},
857 \\"p\q\'r", $foo, $fuz];
863 $bar = eval(Dumper($boo));
865 print Dumper($boo), Dumper($bar); # pretty print (no array indices)
867 $Data::Dumper::Terse = 1; # don't output names where feasible
868 $Data::Dumper::Indent = 0; # turn off all pretty print
869 print Dumper($boo), "\n";
871 $Data::Dumper::Indent = 1; # mild pretty print
874 $Data::Dumper::Indent = 3; # pretty print with array indices
877 $Data::Dumper::Useqq = 1; # print strings in double quotes
882 # recursive structures
892 print Data::Dumper->Dump([$a,$b,$c], [qw(a b c)]);
895 $Data::Dumper::Purity = 1; # fill in the holes for eval
896 print Data::Dumper->Dump([$a, $b], [qw(*a b)]); # print as @a
897 print Data::Dumper->Dump([$b, $a], [qw(*b a)]); # print as %b
900 $Data::Dumper::Deepcopy = 1; # avoid cross-refs
901 print Data::Dumper->Dump([$b, $a], [qw(*b a)]);
904 $Data::Dumper::Purity = 0; # avoid cross-refs
905 print Data::Dumper->Dump([$b, $a], [qw(*b a)]);
909 # object-oriented usage
912 $d = Data::Dumper->new([$a,$b], [qw(a b)]);
913 $d->Seen({'*c' => $c}); # stash a ref without printing it
916 $d->Reset->Purity(0); # empty the seen cache
917 print join "----\n", $d->Dump;
925 sub new { bless { state => 'awake' }, shift }
928 print STDERR "preparing to sleep\n";
929 $s->{state} = 'asleep';
930 return bless $s, 'Foo::ZZZ';
936 print STDERR "waking up\n";
937 $s->{state} = 'awake';
938 return bless $s, 'Foo';
944 $b = Data::Dumper->new([$a], ['c']);
945 $b->Freezer('Freeze');
950 print Data::Dumper->Dump([$d], ['d']);
954 # symbol substitution (useful for recreating CODE refs)
957 sub foo { print "foo speaking\n" }
960 $d = Data::Dumper->new([\&other,$bar],['*other','bar']);
961 $d->Seen({ '*foo' => \&foo });
967 Due to limitations of Perl subroutine call semantics, you cannot pass an
968 array or hash. Prepend it with a C<\> to pass its reference instead. This
969 will be remedied in time, with the arrival of prototypes in later versions
970 of Perl. For now, you need to use the extended usage form, and prepend the
971 name with a C<*> to output it as a hash or array.
973 C<Data::Dumper> cheats with CODE references. If a code reference is
974 encountered in the structure being processed, an anonymous subroutine that
975 contains the string '"DUMMY"' will be inserted in its place, and a warning
976 will be printed if C<Purity> is set. You can C<eval> the result, but bear
977 in mind that the anonymous sub that gets created is just a placeholder.
978 Someday, perl will have a switch to cache-on-demand the string
979 representation of a compiled piece of code, I hope. If you have prior
980 knowledge of all the code refs that your data structures are likely
981 to have, you can use the C<Seen> method to pre-seed the internal reference
982 table and make the dumped output point to them, instead. See L<EXAMPLES>
985 The C<Useqq> flag is not honored by C<Dumpxs()> (it always outputs
986 strings in single quotes).
988 SCALAR objects have the weirdest looking C<bless> workaround.
993 Gurusamy Sarathy gsar@umich.edu
995 Copyright (c) 1996-98 Gurusamy Sarathy. All rights reserved.
996 This program is free software; you can redistribute it and/or
997 modify it under the same terms as Perl itself.
1002 Version 2.10 (31 Oct 1998)