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 $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') {
329 $out .= 'sub { "DUMMY" }';
330 carp "Encountered CODE ref, using dummy placeholder" if $s->{purity};
333 croak "Can\'t handle $realtype type.";
336 if ($realpack) { # we have a blessed ref
337 $out .= ', \'' . $realpack . '\'' . ' )';
338 $out .= '->' . $s->{toaster} . '()' if $s->{toaster} ne '';
339 $s->{apad} = $blesspad;
344 else { # simple scalar
347 # first, catalog the scalar
349 ($id) = ("$ref" =~ /\(([^\(]*)\)$/);
350 if (exists $s->{seen}{$id}) {
351 if ($s->{seen}{$id}[2]) {
352 $out = $s->{seen}{$id}[0];
358 #warn "[>\\$name]\n";
359 $s->{seen}{$id} = ["\\$name", $ref];
362 if (ref($ref) eq 'GLOB' or "$ref" =~ /=GLOB\([^()]+\)$/) { # glob
363 my $name = substr($val, 1);
364 if ($name =~ /^[A-Za-z_][\w:]*$/) {
365 $name =~ s/^main::/::/;
369 $sname = $s->_dump($name, "");
370 $sname = '{' . $sname . '}';
374 local ($s->{level}) = 0;
375 for $k (qw(SCALAR ARRAY HASH)) {
376 my $gval = *$val{$k};
377 next unless defined $gval;
378 next if $k eq "SCALAR" && ! defined $$gval; # always there
380 # _dump can push into @post, so we hold our place using $postlen
381 my $postlen = scalar @post;
382 $post[$postlen] = "\*$sname = ";
383 local ($s->{apad}) = " " x length($post[$postlen]) if $s->{indent} >= 2;
384 $post[$postlen] .= $s->_dump($gval, "\*$sname\{$k\}");
387 $out .= '*' . $sname;
389 elsif (!defined($val)) {
392 elsif ($val =~ /^-?[1-9]\d{0,8}$/) { # safe decimal number
397 $out .= qquote($val, $s->{useqq});
400 $val =~ s/([\\\'])/\\$1/g;
401 $out .= '\'' . $val . '\'';
406 # if we made it this far, $id was added to seen list at current
407 # level, so remove it to get deep copies
408 if ($s->{deepcopy}) {
409 delete($s->{seen}{$id});
412 $s->{seen}{$id}[2] = 1;
419 # non-OO style of earlier version
422 return Data::Dumper->Dump([@_]);
426 # same, only calls the XS version
429 return Data::Dumper->Dumpxs([@_], []);
432 sub Dumpf { return Data::Dumper->Dump(@_) }
434 sub Dumpp { print Data::Dumper->Dump(@_) }
437 # reset the "seen" cache
466 defined($v) ? (($s->{pad} = $v), return $s) : $s->{pad};
471 defined($v) ? (($s->{varname} = $v), return $s) : $s->{varname};
476 defined($v) ? (($s->{purity} = $v), return $s) : $s->{purity};
481 defined($v) ? (($s->{useqq} = $v), return $s) : $s->{useqq};
486 defined($v) ? (($s->{terse} = $v), return $s) : $s->{terse};
491 defined($v) ? (($s->{freezer} = $v), return $s) : $s->{freezer};
496 defined($v) ? (($s->{toaster} = $v), return $s) : $s->{toaster};
501 defined($v) ? (($s->{deepcopy} = $v), return $s) : $s->{deepcopy};
506 defined($v) ? (($s->{quotekeys} = $v), return $s) : $s->{quotekeys};
511 defined($v) ? (($s->{'bless'} = $v), return $s) : $s->{'bless'};
514 # used by qquote below
525 # put a string value in double quotes
528 s/([\\\"\@\$])/\\$1/g;
529 return qq("$_") unless /[^\040-\176]/; # fast exit
531 my $high = shift || "";
532 s/([\a\b\t\n\f\r\e])/$esc{$1}/g;
534 # no need for 3 digits in escape for these
535 s/([\0-\037])(?!\d)/'\\'.sprintf('%o',ord($1))/eg;
537 s/([\0-\037\177])/'\\'.sprintf('%03o',ord($1))/eg;
538 if ($high eq "iso8859") {
539 s/([\200-\240])/'\\'.sprintf('%o',ord($1))/eg;
540 } elsif ($high eq "utf8") {
542 # $str =~ s/([^\040-\176])/sprintf "\\x{%04x}", ord($1)/ge;
543 } elsif ($high eq "8bit") {
546 s/([\0-\037\177-\377])/'\\'.sprintf('%03o',ord($1))/eg;
556 Data::Dumper - stringified perl data structures, suitable for both printing and C<eval>
563 # simple procedural interface
564 print Dumper($foo, $bar);
566 # extended usage with names
567 print Data::Dumper->Dump([$foo, $bar], [qw(foo *ary)]);
569 # configuration variables
571 local $Data::Dump::Purity = 1;
572 eval Data::Dumper->Dump([$foo, $bar], [qw(foo *ary)]);
576 $d = Data::Dumper->new([$foo, $bar], [qw(foo *ary)]);
580 $d->Purity(1)->Terse(1)->Deepcopy(1);
586 Given a list of scalars or reference variables, writes out their contents in
587 perl syntax. The references can also be objects. The contents of each
588 variable is output in a single Perl statement. Handles self-referential
589 structures correctly.
591 The return value can be C<eval>ed to get back an identical copy of the
592 original reference structure.
594 Any references that are the same as one of those passed in will be named
595 C<$VAR>I<n> (where I<n> is a numeric suffix), and other duplicate references
596 to substructures within C<$VAR>I<n> will be appropriately labeled using arrow
597 notation. You can specify names for individual values to be dumped if you
598 use the C<Dump()> method, or you can change the default C<$VAR> prefix to
599 something else. See C<$Data::Dumper::Varname> and C<$Data::Dumper::Terse>
602 The default output of self-referential structures can be C<eval>ed, but the
603 nested references to C<$VAR>I<n> will be undefined, since a recursive
604 structure cannot be constructed using one Perl statement. You should set the
605 C<Purity> flag to 1 to get additional statements that will correctly fill in
608 In the extended usage form, the references to be dumped can be given
609 user-specified names. If a name begins with a C<*>, the output will
610 describe the dereferenced type of the supplied reference for hashes and
611 arrays, and coderefs. Output of names will be avoided where possible if
612 the C<Terse> flag is set.
614 In many cases, methods that are used to set the internal state of the
615 object will return the object itself, so method calls can be conveniently
618 Several styles of output are possible, all controlled by setting
619 the C<Indent> flag. See L<Configuration Variables or Methods> below
627 =item I<PACKAGE>->new(I<ARRAYREF [>, I<ARRAYREF]>)
629 Returns a newly created C<Data::Dumper> object. The first argument is an
630 anonymous array of values to be dumped. The optional second argument is an
631 anonymous array of names for the values. The names need not have a leading
632 C<$> sign, and must be comprised of alphanumeric characters. You can begin
633 a name with a C<*> to specify that the dereferenced type must be dumped
634 instead of the reference itself, for ARRAY and HASH references.
636 The prefix specified by C<$Data::Dumper::Varname> will be used with a
637 numeric suffix if the name for a value is undefined.
639 Data::Dumper will catalog all references encountered while dumping the
640 values. Cross-references (in the form of names of substructures in perl
641 syntax) will be inserted at all possible points, preserving any structural
642 interdependencies in the original set of values. Structure traversal is
643 depth-first, and proceeds in order from the first supplied value to
646 =item I<$OBJ>->Dump I<or> I<PACKAGE>->Dump(I<ARRAYREF [>, I<ARRAYREF]>)
648 Returns the stringified form of the values stored in the object (preserving
649 the order in which they were supplied to C<new>), subject to the
650 configuration options below. In an array context, it returns a list
651 of strings corresponding to the supplied values.
653 The second form, for convenience, simply calls the C<new> method on its
654 arguments before dumping the object immediately.
656 =item I<$OBJ>->Dumpxs I<or> I<PACKAGE>->Dumpxs(I<ARRAYREF [>, I<ARRAYREF]>)
658 This method is available if you were able to compile and install the XSUB
659 extension to C<Data::Dumper>. It is exactly identical to the C<Dump> method
660 above, only about 4 to 5 times faster, since it is written entirely in C.
662 =item I<$OBJ>->Seen(I<[HASHREF]>)
664 Queries or adds to the internal table of already encountered references.
665 You must use C<Reset> to explicitly clear the table if needed. Such
666 references are not dumped; instead, their names are inserted wherever they
667 are encountered subsequently. This is useful especially for properly
668 dumping subroutine references.
670 Expects a anonymous hash of name => value pairs. Same rules apply for names
671 as in C<new>. If no argument is supplied, will return the "seen" list of
672 name => value pairs, in an array context. Otherwise, returns the object
675 =item I<$OBJ>->Values(I<[ARRAYREF]>)
677 Queries or replaces the internal array of values that will be dumped.
678 When called without arguments, returns the values. Otherwise, returns the
681 =item I<$OBJ>->Names(I<[ARRAYREF]>)
683 Queries or replaces the internal array of user supplied names for the values
684 that will be dumped. When called without arguments, returns the names.
685 Otherwise, returns the object itself.
689 Clears the internal table of "seen" references and returns the object
698 =item Dumper(I<LIST>)
700 Returns the stringified form of the values in the list, subject to the
701 configuration options below. The values will be named C<$VAR>I<n> in the
702 output, where I<n> is a numeric suffix. Will return a list of strings
705 =item DumperX(I<LIST>)
707 Identical to the C<Dumper()> function above, but this calls the XSUB
708 implementation. Only available if you were able to compile and install
709 the XSUB extensions in C<Data::Dumper>.
713 =head2 Configuration Variables or Methods
715 Several configuration variables can be used to control the kind of output
716 generated when using the procedural interface. These variables are usually
717 C<local>ized in a block so that other parts of the code are not affected by
720 These variables determine the default state of the object created by calling
721 the C<new> method, but cannot be used to alter the state of the object
722 thereafter. The equivalent method names should be used instead to query
723 or set the internal state of the object.
725 The method forms return the object itself when called with arguments,
726 so that they can be chained together nicely.
730 =item $Data::Dumper::Indent I<or> I<$OBJ>->Indent(I<[NEWVAL]>)
732 Controls the style of indentation. It can be set to 0, 1, 2 or 3. Style 0
733 spews output without any newlines, indentation, or spaces between list
734 items. It is the most compact format possible that can still be called
735 valid perl. Style 1 outputs a readable form with newlines but no fancy
736 indentation (each level in the structure is simply indented by a fixed
737 amount of whitespace). Style 2 (the default) outputs a very readable form
738 which takes into account the length of hash keys (so the hash value lines
739 up). Style 3 is like style 2, but also annotates the elements of arrays
740 with their index (but the comment is on its own line, so array output
741 consumes twice the number of lines). Style 2 is the default.
743 =item $Data::Dumper::Purity I<or> I<$OBJ>->Purity(I<[NEWVAL]>)
745 Controls the degree to which the output can be C<eval>ed to recreate the
746 supplied reference structures. Setting it to 1 will output additional perl
747 statements that will correctly recreate nested references. The default is
750 =item $Data::Dumper::Pad I<or> I<$OBJ>->Pad(I<[NEWVAL]>)
752 Specifies the string that will be prefixed to every line of the output.
753 Empty string by default.
755 =item $Data::Dumper::Varname I<or> I<$OBJ>->Varname(I<[NEWVAL]>)
757 Contains the prefix to use for tagging variable names in the output. The
760 =item $Data::Dumper::Useqq I<or> I<$OBJ>->Useqq(I<[NEWVAL]>)
762 When set, enables the use of double quotes for representing string values.
763 Whitespace other than space will be represented as C<[\n\t\r]>, "unsafe"
764 characters will be backslashed, and unprintable characters will be output as
765 quoted octal integers. Since setting this variable imposes a performance
766 penalty, the default is 0. The C<Dumpxs()> method does not honor this
769 =item $Data::Dumper::Terse I<or> I<$OBJ>->Terse(I<[NEWVAL]>)
771 When set, Data::Dumper will emit single, non-self-referential values as
772 atoms/terms rather than statements. This means that the C<$VAR>I<n> names
773 will be avoided where possible, but be advised that such output may not
774 always be parseable by C<eval>.
776 =item $Data::Dumper::Freezer I<or> $I<OBJ>->Freezer(I<[NEWVAL]>)
778 Can be set to a method name, or to an empty string to disable the feature.
779 Data::Dumper will invoke that method via the object before attempting to
780 stringify it. This method can alter the contents of the object (if, for
781 instance, it contains data allocated from C), and even rebless it in a
782 different package. The client is responsible for making sure the specified
783 method can be called via the object, and that the object ends up containing
784 only perl data types after the method has been called. Defaults to an empty
787 =item $Data::Dumper::Toaster I<or> $I<OBJ>->Toaster(I<[NEWVAL]>)
789 Can be set to a method name, or to an empty string to disable the feature.
790 Data::Dumper will emit a method call for any objects that are to be dumped
791 using the syntax C<bless(DATA, CLASS)->METHOD()>. Note that this means that
792 the method specified will have to perform any modifications required on the
793 object (like creating new state within it, and/or reblessing it in a
794 different package) and then return it. The client is responsible for making
795 sure the method can be called via the object, and that it returns a valid
796 object. Defaults to an empty string.
798 =item $Data::Dumper::Deepcopy I<or> $I<OBJ>->Deepcopy(I<[NEWVAL]>)
800 Can be set to a boolean value to enable deep copies of structures.
801 Cross-referencing will then only be done when absolutely essential
802 (i.e., to break reference cycles). Default is 0.
804 =item $Data::Dumper::Quotekeys I<or> $I<OBJ>->Quotekeys(I<[NEWVAL]>)
806 Can be set to a boolean value to control whether hash keys are quoted.
807 A false value will avoid quoting hash keys when it looks like a simple
808 string. Default is 1, which will always enclose hash keys in quotes.
810 =item $Data::Dumper::Bless I<or> $I<OBJ>->Bless(I<[NEWVAL]>)
812 Can be set to a string that specifies an alternative to the C<bless>
813 builtin operator used to create objects. A function with the specified
814 name should exist, and should accept the same arguments as the builtin.
829 Run these code snippets to get a quick feel for the behavior of this
830 module. When you are through with these examples, you may want to
831 add or change the various configuration variables described above,
832 to see their behavior. (See the testsuite in the Data::Dumper
833 distribution for more examples.)
839 sub new {bless {'a' => 1, 'b' => sub { return "foo" }}, $_[0]};
841 package Fuz; # a weird REF-REF-SCALAR object
842 sub new {bless \($_ = \ 'fu\'z'), $_[0]};
847 $boo = [ 1, [], "abcd", \*foo,
848 {1 => 'a', 023 => 'b', 0x45 => 'c'},
849 \\"p\q\'r", $foo, $fuz];
855 $bar = eval(Dumper($boo));
857 print Dumper($boo), Dumper($bar); # pretty print (no array indices)
859 $Data::Dumper::Terse = 1; # don't output names where feasible
860 $Data::Dumper::Indent = 0; # turn off all pretty print
861 print Dumper($boo), "\n";
863 $Data::Dumper::Indent = 1; # mild pretty print
866 $Data::Dumper::Indent = 3; # pretty print with array indices
869 $Data::Dumper::Useqq = 1; # print strings in double quotes
874 # recursive structures
884 print Data::Dumper->Dump([$a,$b,$c], [qw(a b c)]);
887 $Data::Dumper::Purity = 1; # fill in the holes for eval
888 print Data::Dumper->Dump([$a, $b], [qw(*a b)]); # print as @a
889 print Data::Dumper->Dump([$b, $a], [qw(*b a)]); # print as %b
892 $Data::Dumper::Deepcopy = 1; # avoid cross-refs
893 print Data::Dumper->Dump([$b, $a], [qw(*b a)]);
896 $Data::Dumper::Purity = 0; # avoid cross-refs
897 print Data::Dumper->Dump([$b, $a], [qw(*b a)]);
901 # object-oriented usage
904 $d = Data::Dumper->new([$a,$b], [qw(a b)]);
905 $d->Seen({'*c' => $c}); # stash a ref without printing it
908 $d->Reset->Purity(0); # empty the seen cache
909 print join "----\n", $d->Dump;
917 sub new { bless { state => 'awake' }, shift }
920 print STDERR "preparing to sleep\n";
921 $s->{state} = 'asleep';
922 return bless $s, 'Foo::ZZZ';
928 print STDERR "waking up\n";
929 $s->{state} = 'awake';
930 return bless $s, 'Foo';
936 $b = Data::Dumper->new([$a], ['c']);
937 $b->Freezer('Freeze');
942 print Data::Dumper->Dump([$d], ['d']);
946 # symbol substitution (useful for recreating CODE refs)
949 sub foo { print "foo speaking\n" }
952 $d = Data::Dumper->new([\&other,$bar],['*other','bar']);
953 $d->Seen({ '*foo' => \&foo });
959 Due to limitations of Perl subroutine call semantics, you cannot pass an
960 array or hash. Prepend it with a C<\> to pass its reference instead. This
961 will be remedied in time, with the arrival of prototypes in later versions
962 of Perl. For now, you need to use the extended usage form, and prepend the
963 name with a C<*> to output it as a hash or array.
965 C<Data::Dumper> cheats with CODE references. If a code reference is
966 encountered in the structure being processed, an anonymous subroutine that
967 contains the string '"DUMMY"' will be inserted in its place, and a warning
968 will be printed if C<Purity> is set. You can C<eval> the result, but bear
969 in mind that the anonymous sub that gets created is just a placeholder.
970 Someday, perl will have a switch to cache-on-demand the string
971 representation of a compiled piece of code, I hope. If you have prior
972 knowledge of all the code refs that your data structures are likely
973 to have, you can use the C<Seen> method to pre-seed the internal reference
974 table and make the dumped output point to them, instead. See L<EXAMPLES>
977 The C<Useqq> flag is not honored by C<Dumpxs()> (it always outputs
978 strings in single quotes).
980 SCALAR objects have the weirdest looking C<bless> workaround.
985 Gurusamy Sarathy gsar@umich.edu
987 Copyright (c) 1996-98 Gurusamy Sarathy. All rights reserved.
988 This program is free software; you can redistribute it and/or
989 modify it under the same terms as Perl itself.
994 Version 2.10 (31 Oct 1998)