1Data::Dump(3) User Contributed Perl Documentation Data::Dump(3)
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6 Data::Dump - Pretty printing of data structures
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9 use Data::Dump qw(dump ddx);
10 $str = dump(@list);
12 @copy_of_list = eval $str;
13 # or use it for easy debug printout
15 ddx localtime;
16
18 This module provide functions that takes a list of values as their
19 argument and produces a string as its result. The string contains Perl
20 code that, when "eval"ed, produces a deep copy of the original
21 arguments.
22 The main feature of the module is that it strives to produce output
24 that is easy to read. Example:
25 @a = (1, [2, 3], {4 => 5});
27 dump(@a);
28 Produces:
30 (1, [2, 3], { 4 => 5 })
32 If you dump just a little data, it is output on a single line. If you
34 dump data that is more complex or there is a lot of it, line breaks are
35 automatically added to keep it easy to read.
36 The following functions are provided (only the dd* functions are
38 exported by default):
39 dump( ... )
41 pp( ... )
42 Returns a string containing a Perl expression. If you pass this
43 string to Perl's built-in eval() function it should return a copy
44 of the arguments you passed to dump().
45 If you call the function with multiple arguments then the output
47 will be wrapped in parenthesis "( ..., ... )". If you call the
48 function with a single argument the output will not have the
49 wrapping. If you call the function with a single scalar (non-
50 reference) argument it will just return the scalar quoted if
51 needed, but never break it into multiple lines. If you pass
52 multiple arguments or references to arrays of hashes then the
53 return value might contain line breaks to format it for easier
54 reading. The returned string will never be "\n" terminated, even
55 if contains multiple lines. This allows code like this to place
56 the semicolon in the expected place:
57 print '$obj = ', dump($obj), ";\n";
59 If dump() is called in void context, then the dump is printed on
61 STDERR and then "\n" terminated. You might find this useful for
62 quick debug printouts, but the dd*() functions might be better
63 alternatives for this.
64 There is no difference between dump() and pp(), except that dump()
66 shares its name with a not-so-useful perl builtin. Because of this
67 some might want to avoid using that name.
68 quote( $string )
70 Returns a quoted version of the provided string.
71 It differs from "dump($string)" in that it will quote even numbers
73 and not try to come up with clever expressions that might shorten
74 the output.
75 dd( ... )
77 ddx( ... )
78 These functions will call dump() on their argument and print the
79 result to STDOUT (actually, it's the currently selected output
80 handle, but STDOUT is the default for that).
81 The difference between them is only that ddx() will prefix the
83 lines it prints with "# " and mark the first line with the file and
84 line number where it was called. This is meant to be useful for
85 debug printouts of state within programs.
86
88 Code references will be displayed as simply 'sub { "???" }' when
89 dumped. Thus, "eval"ing them will not reproduce the original routine.
90 If you forget to explicitly import the "dump" function, your code will
92 core dump. That's because you just called the builtin "dump" function
93 by accident, which intentionally dumps core. Because of this you can
94 also import the same function as "pp", mnemonic for "pretty-print".
95
97 The "Data::Dump" module grew out of frustration with Sarathy's in-most-
98 cases-excellent "Data::Dumper". Basic ideas and some code are shared
99 with Sarathy's module.
100 The "Data::Dump" module provides a much simpler interface than
102 "Data::Dumper". No OO interface is available and there are no
103 configuration options to worry about (yet :-). The other benefit is
104 that the dump produced does not try to set any variables. It only
105 returns what is needed to produce a copy of the arguments. This means
106 that "dump("foo")" simply returns "foo", and "dump(1..5)" simply
107 returns "(1, 2, 3, 4, 5)".
108
110 Data::Dumper, Storable
111
113 The "Data::Dump" module is written by Gisle Aas <gisle@aas.no>, based
114 on "Data::Dumper" by Gurusamy Sarathy <gsar@umich.edu>.
115 Copyright 1998-2000,2003-2004,2008 Gisle Aas.
117 Copyright 1996-1998 Gurusamy Sarathy.
118 This library is free software; you can redistribute it and/or modify it
120 under the same terms as Perl itself.
121perl v5.12.0 2009-07-26 Data::Dump(3)