Data::Dump(3) User Contributed Perl Documentation Data::Dump(3)
NAME
Data::Dump - Pretty printing of data structures
SYNOPSIS
use Data::Dump qw(dump);
$str = dump(@list);
@copy_of_list = eval $str;
# or use it for easy debug printout
use Data::Dump; dd localtime;
DESCRIPTION
This module provides a few functions that traverse their argument list
and return a string containing Perl code that, when "eval"ed, produces
a deep copy of the original arguments.
The main feature of the module is that it strives to produce output
that is easy to read. Example:
@a = (1, [2, 3], {4 => 5});
dump(@a);
Produces:
"(1, [2, 3], { 4 => 5 })"
If you dump just a little data, it is output on a single line. If you
dump data that is more complex or there is a lot of it, line breaks are
automatically added to keep it easy to read.
The following functions are provided (only the dd* functions are
exported by default):
dump( ... )
pp( ... )
Returns a string containing a Perl expression. If you pass this
string to Perl's built-in eval() function it should return a copy
of the arguments you passed to dump().
If you call the function with multiple arguments then the output
will be wrapped in parenthesis "( ..., ... )". If you call the
function with a single argument the output will not have the
wrapping. If you call the function with a single scalar (non-
reference) argument it will just return the scalar quoted if
needed, but never break it into multiple lines. If you pass
multiple arguments or references to arrays of hashes then the
return value might contain line breaks to format it for easier
reading. The returned string will never be "\n" terminated, even
if contains multiple lines. This allows code like this to place
the semicolon in the expected place:
print '$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.
quote( $string )
Returns a quoted version of the provided string.
It differs from "dump($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.
dd( ... )
ddx( ... )
These functions will call 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.
dumpf( ..., \&filter )
Short hand for calling the dump_filtered() function of
Data::Dump::Filtered. 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.
CONFIGURATION
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.
$Data::Dump::INDENT
This holds the string that's used for indenting multiline data
structures. It's default value is " " (two spaces). Set it to ""
to suppress indentation. Setting it to "| " makes for nice visuals
even if the dump output then fails to be valid Perl.
$Data::Dump::TRY_BASE64
How long must a binary string be before we try to use the base64
encoding for the dump output. The default is 50. Set it to 0 to
disable base64 dumps.
$Data::Dump::LINEWIDTH
This controls how wide the string should before we add a line
break. The default is 60.
LIMITATIONS
Code references will be dumped as "sub { ... }". Thus, "eval"ing 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".
HISTORY
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)'.
SEE ALSO
Data::Dump::Filtered(3), Data::Dump::Trace(3), Data::Dumper(3), JSON(3),
Storable(3)
AUTHORS
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 distribution is currenly maintained by Breno G. de Oliveira.
This library is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
perl v5.30.3 2021-06-26 Data::Dump(3)
data-dump 1.250.0 - Generated Wed Jul 14 15:54:44 CDT 2021