| Data::Dump - Pretty printing of data structures |
Data::Dump - Pretty printing of data structures
use Data::Dump qw(dump);
$str = dump(@list); @copy_of_list = eval $str;
# or use it for easy debug printout use Data::Dump; dd localtime;
This module provide a few functions that traverse their
argument and produces a string as its result. The string contains
Perl code that, when evaled, produces a deep copy of the original
arguments.
The main feature of the module is that it strives to produce output that is easy to read. Example:
@a = (1, [2, 3], {4 => 5});
dump(@a);
Produces:
"(1, [2, 3], { 4 => 5 })"
If you dump just a little data, it is output on a single line. If you dump data that is more complex or there is a lot of it, line breaks are automatically added to keep it easy to read.
The following functions are provided (only the dd* functions are exported by default):
eval() function it should return a copy of
the arguments you passed to dump().
If you call the function with multiple arguments then the output will be wrapped in parenthesis ``( ..., ... )''. If you call the function with a single argument the output will not have the wrapping. If you call the function with a single scalar (non-reference) argument it will just return the scalar quoted if needed, but never break it into multiple lines. If you pass multiple arguments or references to arrays of hashes then the return value might contain line breaks to format it for easier reading. The returned string will never be ``\n'' terminated, even if contains multiple lines. This allows code like this to place the semicolon in the expected place:
print '$obj = ', dump($obj), ";\n";
If dump() is called in void context, then the dump is printed on
STDERR and then ``\n'' terminated. You might find this useful for quick
debug printouts, but the dd*() functions might be better alternatives
for this.
There is no difference between dump() and pp(), except that dump()
shares its name with a not-so-useful perl builtin. Because of this
some might want to avoid using that name.
It differs from dump($string) in that it will quote even numbers and
not try to come up with clever expressions that might shorten the
output. If a non-scalar argument is provided then it's just stringified
instead of traversed.
dump() on their argument and print the
result to STDOUT (actually, it's the currently selected output handle, but
STDOUT is the default for that).
The difference between them is only that ddx() will prefix the lines
it prints with ``# '' and mark the first line with the file and line
number where it was called. This is meant to be useful for debug
printouts of state within programs.
dump_filtered() function of the Data::Dump::Filtered manpage.
This works like dump(), but the last argument should be a filter callback
function. As objects are visited the filter callback is invoked and it
can modify how the objects are dumped.
There are a few global variables that can be set to modify the output generated by the dump functions. It's wise to localize the setting of these.
Code references will be dumped as sub { ... }. Thus, evaling them will
not reproduce the original routine. The ...-operator used will also require
perl-5.12 or better to be evaled.
If you forget to explicitly import the dump function, your code will
core dump. That's because you just called the builtin dump function
by accident, which intentionally dumps core. Because of this you can
also import the same function as pp, mnemonic for ``pretty-print''.
The Data::Dump module grew out of frustration with Sarathy's
in-most-cases-excellent Data::Dumper. Basic ideas and some code
are shared with Sarathy's module.
The Data::Dump module provides a much simpler interface than
Data::Dumper. No OO interface is available and there are fewer
configuration options to worry about. The other benefit is
that the dump produced does not try to set any variables. It only
returns what is needed to produce a copy of the arguments. This means
that dump("foo") simply returns '"foo"', and dump(1..3) simply
returns '(1, 2, 3)'.
the Data::Dump::Filtered manpage, the Data::Dump::Trace manpage, the Data::Dumper manpage, JSON, the Storable manpage
The Data::Dump module is written by Gisle Aas <gisle@aas.no>, based
on Data::Dumper by Gurusamy Sarathy <gsar@umich.edu>.
Copyright 1998-2010 Gisle Aas. Copyright 1996-1998 Gurusamy Sarathy.
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
| Data::Dump - Pretty printing of data structures |