4 # convert perl data structures into perl syntax suitable for both printing
7 # Documentation at the __END__
12 $VERSION = $VERSION = '2.10';
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 $ipad = $s->{xpad} x $s->{level};
265 if ($realpack) { # we have a blessed ref
266 $out = $s->{'bless'} . '( ';
267 $blesspad = $s->{apad};
268 $s->{apad} .= ' ' if ($s->{indent} >= 2);
271 if ($realtype eq 'SCALAR') {
273 $out .= 'do{\\(my $o = ' . $s->_dump($$val, "\${$name}") . ')}';
276 $out .= '\\' . $s->_dump($$val, "\${$name}");
279 elsif ($realtype eq 'GLOB') {
280 $out .= '\\' . $s->_dump($$val, "*{$name}");
282 elsif ($realtype eq 'ARRAY') {
283 my($v, $pad, $mname);
285 $out .= ($name =~ /^\@/) ? '(' : '[';
286 $pad = $s->{sep} . $s->{pad} . $s->{apad};
287 ($name =~ /^\@(.*)$/) ? ($mname = "\$" . $1) :
288 # omit -> if $foo->[0]->{bar}, but not ${$foo->[0]}->{bar}
289 ($name =~ /^\\?[\%\@\*\$][^{].*[]}]$/) ? ($mname = $name) :
290 ($mname = $name . '->');
291 $mname .= '->' if $mname =~ /^\*.+\{[A-Z]+\}$/;
293 $sname = $mname . '[' . $i . ']';
294 $out .= $pad . $ipad . '#' . $i if $s->{indent} >= 3;
295 $out .= $pad . $ipad . $s->_dump($v, $sname);
296 $out .= "," if $i++ < $#$val;
298 $out .= $pad . ($s->{xpad} x ($s->{level} - 1)) if $i;
299 $out .= ($name =~ /^\@/) ? ')' : ']';
301 elsif ($realtype eq 'HASH') {
302 my($k, $v, $pad, $lpad, $mname);
303 $out .= ($name =~ /^\%/) ? '(' : '{';
304 $pad = $s->{sep} . $s->{pad} . $s->{apad};
306 ($name =~ /^\%(.*)$/) ? ($mname = "\$" . $1) :
307 # omit -> if $foo->[0]->{bar}, but not ${$foo->[0]}->{bar}
308 ($name =~ /^\\?[\%\@\*\$][^{].*[]}]$/) ? ($mname = $name) :
309 ($mname = $name . '->');
310 $mname .= '->' if $mname =~ /^\*.+\{[A-Z]+\}$/;
311 while (($k, $v) = each %$val) {
312 my $nk = $s->_dump($k, "");
313 $nk = $1 if !$s->{quotekeys} and $nk =~ /^[\"\']([A-Za-z_]\w*)[\"\']$/;
314 $sname = $mname . '{' . $nk . '}';
315 $out .= $pad . $ipad . $nk . " => ";
317 # temporarily alter apad
318 $s->{apad} .= (" " x (length($nk) + 4)) if $s->{indent} >= 2;
319 $out .= $s->_dump($val->{$k}, $sname) . ",";
320 $s->{apad} = $lpad if $s->{indent} >= 2;
322 if (substr($out, -1) eq ',') {
324 $out .= $pad . ($s->{xpad} x ($s->{level} - 1));
326 $out .= ($name =~ /^\%/) ? ')' : '}';
328 elsif ($realtype eq 'CODE') {
330 $out = 'sub { ' . $out . ' }';
331 carp "Encountered CODE ref, using dummy placeholder" if $s->{purity};
334 croak "Can\'t handle $realtype type.";
337 if ($realpack) { # we have a blessed ref
338 $out .= ', \'' . $realpack . '\'' . ' )';
339 $out .= '->' . $s->{toaster} . '()' if $s->{toaster} ne '';
340 $s->{apad} = $blesspad;
345 else { # simple scalar
348 # first, catalog the scalar
350 ($id) = ("$ref" =~ /\(([^\(]*)\)$/);
351 if (exists $s->{seen}{$id}) {
352 if ($s->{seen}{$id}[2]) {
353 $out = $s->{seen}{$id}[0];
359 #warn "[>\\$name]\n";
360 $s->{seen}{$id} = ["\\$name", $ref];
363 if (ref($ref) eq 'GLOB' or "$ref" =~ /=GLOB\([^()]+\)$/) { # glob
364 my $name = substr($val, 1);
365 if ($name =~ /^[A-Za-z_][\w:]*$/) {
366 $name =~ s/^main::/::/;
370 $sname = $s->_dump($name, "");
371 $sname = '{' . $sname . '}';
375 local ($s->{level}) = 0;
376 for $k (qw(SCALAR ARRAY HASH)) {
377 my $gval = *$val{$k};
378 next unless defined $gval;
379 next if $k eq "SCALAR" && ! defined $$gval; # always there
381 # _dump can push into @post, so we hold our place using $postlen
382 my $postlen = scalar @post;
383 $post[$postlen] = "\*$sname = ";
384 local ($s->{apad}) = " " x length($post[$postlen]) if $s->{indent} >= 2;
385 $post[$postlen] .= $s->_dump($gval, "\*$sname\{$k\}");
388 $out .= '*' . $sname;
390 elsif (!defined($val)) {
393 elsif ($val =~ /^-?[1-9]\d{0,8}$/) { # safe decimal number
398 $out .= qquote($val, $s->{useqq});
401 $val =~ s/([\\\'])/\\$1/g;
402 $out .= '\'' . $val . '\'';
407 # if we made it this far, $id was added to seen list at current
408 # level, so remove it to get deep copies
409 if ($s->{deepcopy}) {
410 delete($s->{seen}{$id});
413 $s->{seen}{$id}[2] = 1;
420 # non-OO style of earlier version
423 return Data::Dumper->Dump([@_]);
427 # same, only calls the XS version
430 return Data::Dumper->Dumpxs([@_], []);
433 sub Dumpf { return Data::Dumper->Dump(@_) }
435 sub Dumpp { print Data::Dumper->Dump(@_) }
438 # reset the "seen" cache
467 defined($v) ? (($s->{pad} = $v), return $s) : $s->{pad};
472 defined($v) ? (($s->{varname} = $v), return $s) : $s->{varname};
477 defined($v) ? (($s->{purity} = $v), return $s) : $s->{purity};
482 defined($v) ? (($s->{useqq} = $v), return $s) : $s->{useqq};
487 defined($v) ? (($s->{terse} = $v), return $s) : $s->{terse};
492 defined($v) ? (($s->{freezer} = $v), return $s) : $s->{freezer};
497 defined($v) ? (($s->{toaster} = $v), return $s) : $s->{toaster};
502 defined($v) ? (($s->{deepcopy} = $v), return $s) : $s->{deepcopy};
507 defined($v) ? (($s->{quotekeys} = $v), return $s) : $s->{quotekeys};
512 defined($v) ? (($s->{'bless'} = $v), return $s) : $s->{'bless'};
515 # used by qquote below
526 # put a string value in double quotes
529 s/([\\\"\@\$])/\\$1/g;
530 return qq("$_") unless /[^\040-\176]/; # fast exit
532 my $high = shift || "";
533 s/([\a\b\t\n\f\r\e])/$esc{$1}/g;
535 # no need for 3 digits in escape for these
536 s/([\0-\037])(?!\d)/'\\'.sprintf('%o',ord($1))/eg;
538 s/([\0-\037\177])/'\\'.sprintf('%03o',ord($1))/eg;
539 if ($high eq "iso8859") {
540 s/([\200-\240])/'\\'.sprintf('%o',ord($1))/eg;
541 } elsif ($high eq "utf8") {
543 # $str =~ s/([^\040-\176])/sprintf "\\x{%04x}", ord($1)/ge;
544 } elsif ($high eq "8bit") {
547 s/([\0-\037\177-\377])/'\\'.sprintf('%03o',ord($1))/eg;
557 Data::Dumper - stringified perl data structures, suitable for both printing and C<eval>
564 # simple procedural interface
565 print Dumper($foo, $bar);
567 # extended usage with names
568 print Data::Dumper->Dump([$foo, $bar], [qw(foo *ary)]);
570 # configuration variables
572 local $Data::Dump::Purity = 1;
573 eval Data::Dumper->Dump([$foo, $bar], [qw(foo *ary)]);
577 $d = Data::Dumper->new([$foo, $bar], [qw(foo *ary)]);
581 $d->Purity(1)->Terse(1)->Deepcopy(1);
587 Given a list of scalars or reference variables, writes out their contents in
588 perl syntax. The references can also be objects. The contents of each
589 variable is output in a single Perl statement. Handles self-referential
590 structures correctly.
592 The return value can be C<eval>ed to get back an identical copy of the
593 original reference structure.
595 Any references that are the same as one of those passed in will be named
596 C<$VAR>I<n> (where I<n> is a numeric suffix), and other duplicate references
597 to substructures within C<$VAR>I<n> will be appropriately labeled using arrow
598 notation. You can specify names for individual values to be dumped if you
599 use the C<Dump()> method, or you can change the default C<$VAR> prefix to
600 something else. See C<$Data::Dumper::Varname> and C<$Data::Dumper::Terse>
603 The default output of self-referential structures can be C<eval>ed, but the
604 nested references to C<$VAR>I<n> will be undefined, since a recursive
605 structure cannot be constructed using one Perl statement. You should set the
606 C<Purity> flag to 1 to get additional statements that will correctly fill in
609 In the extended usage form, the references to be dumped can be given
610 user-specified names. If a name begins with a C<*>, the output will
611 describe the dereferenced type of the supplied reference for hashes and
612 arrays, and coderefs. Output of names will be avoided where possible if
613 the C<Terse> flag is set.
615 In many cases, methods that are used to set the internal state of the
616 object will return the object itself, so method calls can be conveniently
619 Several styles of output are possible, all controlled by setting
620 the C<Indent> flag. See L<Configuration Variables or Methods> below
628 =item I<PACKAGE>->new(I<ARRAYREF [>, I<ARRAYREF]>)
630 Returns a newly created C<Data::Dumper> object. The first argument is an
631 anonymous array of values to be dumped. The optional second argument is an
632 anonymous array of names for the values. The names need not have a leading
633 C<$> sign, and must be comprised of alphanumeric characters. You can begin
634 a name with a C<*> to specify that the dereferenced type must be dumped
635 instead of the reference itself, for ARRAY and HASH references.
637 The prefix specified by C<$Data::Dumper::Varname> will be used with a
638 numeric suffix if the name for a value is undefined.
640 Data::Dumper will catalog all references encountered while dumping the
641 values. Cross-references (in the form of names of substructures in perl
642 syntax) will be inserted at all possible points, preserving any structural
643 interdependencies in the original set of values. Structure traversal is
644 depth-first, and proceeds in order from the first supplied value to
647 =item I<$OBJ>->Dump I<or> I<PACKAGE>->Dump(I<ARRAYREF [>, I<ARRAYREF]>)
649 Returns the stringified form of the values stored in the object (preserving
650 the order in which they were supplied to C<new>), subject to the
651 configuration options below. In an array context, it returns a list
652 of strings corresponding to the supplied values.
654 The second form, for convenience, simply calls the C<new> method on its
655 arguments before dumping the object immediately.
657 =item I<$OBJ>->Dumpxs I<or> I<PACKAGE>->Dumpxs(I<ARRAYREF [>, I<ARRAYREF]>)
659 This method is available if you were able to compile and install the XSUB
660 extension to C<Data::Dumper>. It is exactly identical to the C<Dump> method
661 above, only about 4 to 5 times faster, since it is written entirely in C.
663 =item I<$OBJ>->Seen(I<[HASHREF]>)
665 Queries or adds to the internal table of already encountered references.
666 You must use C<Reset> to explicitly clear the table if needed. Such
667 references are not dumped; instead, their names are inserted wherever they
668 are encountered subsequently. This is useful especially for properly
669 dumping subroutine references.
671 Expects a anonymous hash of name => value pairs. Same rules apply for names
672 as in C<new>. If no argument is supplied, will return the "seen" list of
673 name => value pairs, in an array context. Otherwise, returns the object
676 =item I<$OBJ>->Values(I<[ARRAYREF]>)
678 Queries or replaces the internal array of values that will be dumped.
679 When called without arguments, returns the values. Otherwise, returns the
682 =item I<$OBJ>->Names(I<[ARRAYREF]>)
684 Queries or replaces the internal array of user supplied names for the values
685 that will be dumped. When called without arguments, returns the names.
686 Otherwise, returns the object itself.
690 Clears the internal table of "seen" references and returns the object
699 =item Dumper(I<LIST>)
701 Returns the stringified form of the values in the list, subject to the
702 configuration options below. The values will be named C<$VAR>I<n> in the
703 output, where I<n> is a numeric suffix. Will return a list of strings
706 =item DumperX(I<LIST>)
708 Identical to the C<Dumper()> function above, but this calls the XSUB
709 implementation. Only available if you were able to compile and install
710 the XSUB extensions in C<Data::Dumper>.
714 =head2 Configuration Variables or Methods
716 Several configuration variables can be used to control the kind of output
717 generated when using the procedural interface. These variables are usually
718 C<local>ized in a block so that other parts of the code are not affected by
721 These variables determine the default state of the object created by calling
722 the C<new> method, but cannot be used to alter the state of the object
723 thereafter. The equivalent method names should be used instead to query
724 or set the internal state of the object.
726 The method forms return the object itself when called with arguments,
727 so that they can be chained together nicely.
731 =item $Data::Dumper::Indent I<or> I<$OBJ>->Indent(I<[NEWVAL]>)
733 Controls the style of indentation. It can be set to 0, 1, 2 or 3. Style 0
734 spews output without any newlines, indentation, or spaces between list
735 items. It is the most compact format possible that can still be called
736 valid perl. Style 1 outputs a readable form with newlines but no fancy
737 indentation (each level in the structure is simply indented by a fixed
738 amount of whitespace). Style 2 (the default) outputs a very readable form
739 which takes into account the length of hash keys (so the hash value lines
740 up). Style 3 is like style 2, but also annotates the elements of arrays
741 with their index (but the comment is on its own line, so array output
742 consumes twice the number of lines). Style 2 is the default.
744 =item $Data::Dumper::Purity I<or> I<$OBJ>->Purity(I<[NEWVAL]>)
746 Controls the degree to which the output can be C<eval>ed to recreate the
747 supplied reference structures. Setting it to 1 will output additional perl
748 statements that will correctly recreate nested references. The default is
751 =item $Data::Dumper::Pad I<or> I<$OBJ>->Pad(I<[NEWVAL]>)
753 Specifies the string that will be prefixed to every line of the output.
754 Empty string by default.
756 =item $Data::Dumper::Varname I<or> I<$OBJ>->Varname(I<[NEWVAL]>)
758 Contains the prefix to use for tagging variable names in the output. The
761 =item $Data::Dumper::Useqq I<or> I<$OBJ>->Useqq(I<[NEWVAL]>)
763 When set, enables the use of double quotes for representing string values.
764 Whitespace other than space will be represented as C<[\n\t\r]>, "unsafe"
765 characters will be backslashed, and unprintable characters will be output as
766 quoted octal integers. Since setting this variable imposes a performance
767 penalty, the default is 0. The C<Dumpxs()> method does not honor this
770 =item $Data::Dumper::Terse I<or> I<$OBJ>->Terse(I<[NEWVAL]>)
772 When set, Data::Dumper will emit single, non-self-referential values as
773 atoms/terms rather than statements. This means that the C<$VAR>I<n> names
774 will be avoided where possible, but be advised that such output may not
775 always be parseable by C<eval>.
777 =item $Data::Dumper::Freezer I<or> $I<OBJ>->Freezer(I<[NEWVAL]>)
779 Can be set to a method name, or to an empty string to disable the feature.
780 Data::Dumper will invoke that method via the object before attempting to
781 stringify it. This method can alter the contents of the object (if, for
782 instance, it contains data allocated from C), and even rebless it in a
783 different package. The client is responsible for making sure the specified
784 method can be called via the object, and that the object ends up containing
785 only perl data types after the method has been called. Defaults to an empty
788 =item $Data::Dumper::Toaster I<or> $I<OBJ>->Toaster(I<[NEWVAL]>)
790 Can be set to a method name, or to an empty string to disable the feature.
791 Data::Dumper will emit a method call for any objects that are to be dumped
792 using the syntax C<bless(DATA, CLASS)->METHOD()>. Note that this means that
793 the method specified will have to perform any modifications required on the
794 object (like creating new state within it, and/or reblessing it in a
795 different package) and then return it. The client is responsible for making
796 sure the method can be called via the object, and that it returns a valid
797 object. Defaults to an empty string.
799 =item $Data::Dumper::Deepcopy I<or> $I<OBJ>->Deepcopy(I<[NEWVAL]>)
801 Can be set to a boolean value to enable deep copies of structures.
802 Cross-referencing will then only be done when absolutely essential
803 (i.e., to break reference cycles). Default is 0.
805 =item $Data::Dumper::Quotekeys I<or> $I<OBJ>->Quotekeys(I<[NEWVAL]>)
807 Can be set to a boolean value to control whether hash keys are quoted.
808 A false value will avoid quoting hash keys when it looks like a simple
809 string. Default is 1, which will always enclose hash keys in quotes.
811 =item $Data::Dumper::Bless I<or> $I<OBJ>->Bless(I<[NEWVAL]>)
813 Can be set to a string that specifies an alternative to the C<bless>
814 builtin operator used to create objects. A function with the specified
815 name should exist, and should accept the same arguments as the builtin.
830 Run these code snippets to get a quick feel for the behavior of this
831 module. When you are through with these examples, you may want to
832 add or change the various configuration variables described above,
833 to see their behavior. (See the testsuite in the Data::Dumper
834 distribution for more examples.)
840 sub new {bless {'a' => 1, 'b' => sub { return "foo" }}, $_[0]};
842 package Fuz; # a weird REF-REF-SCALAR object
843 sub new {bless \($_ = \ 'fu\'z'), $_[0]};
848 $boo = [ 1, [], "abcd", \*foo,
849 {1 => 'a', 023 => 'b', 0x45 => 'c'},
850 \\"p\q\'r", $foo, $fuz];
856 $bar = eval(Dumper($boo));
858 print Dumper($boo), Dumper($bar); # pretty print (no array indices)
860 $Data::Dumper::Terse = 1; # don't output names where feasible
861 $Data::Dumper::Indent = 0; # turn off all pretty print
862 print Dumper($boo), "\n";
864 $Data::Dumper::Indent = 1; # mild pretty print
867 $Data::Dumper::Indent = 3; # pretty print with array indices
870 $Data::Dumper::Useqq = 1; # print strings in double quotes
875 # recursive structures
885 print Data::Dumper->Dump([$a,$b,$c], [qw(a b c)]);
888 $Data::Dumper::Purity = 1; # fill in the holes for eval
889 print Data::Dumper->Dump([$a, $b], [qw(*a b)]); # print as @a
890 print Data::Dumper->Dump([$b, $a], [qw(*b a)]); # print as %b
893 $Data::Dumper::Deepcopy = 1; # avoid cross-refs
894 print Data::Dumper->Dump([$b, $a], [qw(*b a)]);
897 $Data::Dumper::Purity = 0; # avoid cross-refs
898 print Data::Dumper->Dump([$b, $a], [qw(*b a)]);
902 # object-oriented usage
905 $d = Data::Dumper->new([$a,$b], [qw(a b)]);
906 $d->Seen({'*c' => $c}); # stash a ref without printing it
909 $d->Reset->Purity(0); # empty the seen cache
910 print join "----\n", $d->Dump;
918 sub new { bless { state => 'awake' }, shift }
921 print STDERR "preparing to sleep\n";
922 $s->{state} = 'asleep';
923 return bless $s, 'Foo::ZZZ';
929 print STDERR "waking up\n";
930 $s->{state} = 'awake';
931 return bless $s, 'Foo';
937 $b = Data::Dumper->new([$a], ['c']);
938 $b->Freezer('Freeze');
943 print Data::Dumper->Dump([$d], ['d']);
947 # symbol substitution (useful for recreating CODE refs)
950 sub foo { print "foo speaking\n" }
953 $d = Data::Dumper->new([\&other,$bar],['*other','bar']);
954 $d->Seen({ '*foo' => \&foo });
960 Due to limitations of Perl subroutine call semantics, you cannot pass an
961 array or hash. Prepend it with a C<\> to pass its reference instead. This
962 will be remedied in time, with the arrival of prototypes in later versions
963 of Perl. For now, you need to use the extended usage form, and prepend the
964 name with a C<*> to output it as a hash or array.
966 C<Data::Dumper> cheats with CODE references. If a code reference is
967 encountered in the structure being processed, an anonymous subroutine that
968 contains the string '"DUMMY"' will be inserted in its place, and a warning
969 will be printed if C<Purity> is set. You can C<eval> the result, but bear
970 in mind that the anonymous sub that gets created is just a placeholder.
971 Someday, perl will have a switch to cache-on-demand the string
972 representation of a compiled piece of code, I hope. If you have prior
973 knowledge of all the code refs that your data structures are likely
974 to have, you can use the C<Seen> method to pre-seed the internal reference
975 table and make the dumped output point to them, instead. See L<EXAMPLES>
978 The C<Useqq> flag is not honored by C<Dumpxs()> (it always outputs
979 strings in single quotes).
981 SCALAR objects have the weirdest looking C<bless> workaround.
986 Gurusamy Sarathy gsar@umich.edu
988 Copyright (c) 1996-98 Gurusamy Sarathy. All rights reserved.
989 This program is free software; you can redistribute it and/or
990 modify it under the same terms as Perl itself.
995 Version 2.10 (31 Oct 1998)