YAML::Syck(3)

NAME
YAML::Syck - Fast, lightweight YAML loader and dumper

SYNOPSIS
    use YAML::Syck;

    # Set this for interoperability with other YAML/Syck bindings:
    # e.g. Load('Yes') becomes 1 and Load('No') becomes ''.
    $YAML::Syck::ImplicitTyping = 1;

    $data = Load($yaml);
    $yaml = Dump($data);

    # $file can be an IO object, or a filename
    $data = LoadFile($file);
    DumpFile($file, $data);

    # A string with multiple YAML streams in it
    $yaml = Dump(@data);
    @data = Load($yaml);

    # Dumping into a pre-existing output buffer
    my $yaml;
    DumpInto(\$yaml, @data);

DESCRIPTION
This module provides a Perl interface to the libsyck data serialization library. It exports the "Dump" and "Load" functions for converting Perl data structures to YAML strings, and the other way around.

NOTE: If you are working with other language's YAML/Syck bindings (such as Ruby), please set $YAML::Syck::ImplicitTyping to 1 before calling the "Load"/"Dump" functions. The default setting is for preserving backward-compatibility with "YAML.pm".

Differences Between YAML::Syck and YAML

  Error handling
Some calls are designed to die rather than returning YAML. You should wrap your calls in eval to assure you do not get unexpected results.

FLAGS

  $YAML::Syck::MaxDepth
Maximum nesting depth for "Load" and "Dump". Defaults to 512. "Dump" will "croak" if a data structure exceeds this depth, and "Load" will "croak" if a YAML document is nested deeper than this limit. This prevents stack exhaustion from maliciously crafted input. Increase the value if you legitimately need very deeply nested structures.

  $YAML::Syck::Headless
Defaults to false. Setting this to a true value will make "Dump" omit the leading "---\n" marker.

  $YAML::Syck::SortKeys
Defaults to true (1). Setting this to a true value will make "Dump" sort hash keys.

  $YAML::Syck::SingleQuote
Defaults to false. Setting this to a true value will make "Dump" always emit single quotes instead of bare strings.

  $YAML::Syck::ImplicitTyping
Defaults to false. Setting this to a true value will make "Load" recognize various implicit types in YAML, such as unquoted "true", "false", as well as integers and floating-point numbers. Otherwise, only "~" is recognized to be "undef".

  $YAML::Syck::ImplicitUnicode
Defaults to false. For Perl 5.8.0 or later, setting this to a true value will make "Load" set Unicode flag on for every string that contains valid UTF8 sequences, and make "Dump" return a unicode string.

Regardless of this flag, Unicode strings are dumped verbatim without escaping; byte strings with high-bit set will be dumped with backslash escaping.

However, because YAML does not distinguish between these two kinds of strings, so this flag will affect loading of both variants of strings.

If you want to use LoadFile or DumpFile with unicode, you are required to open your own file in order to assure it's UTF8 encoded:

  open(my $fh, ">:encoding(UTF-8)", "out.yml");
  DumpFile($fh, $hashref);

  $YAML::Syck::ImplicitBinary
Defaults to false. For Perl 5.8.0 or later, setting this to a true value will make "Dump" generate Base64-encoded "!!binary" data for all non-Unicode scalars containing high-bit bytes.

  $YAML::Syck::UseCode / $YAML::Syck::LoadCode / $YAML::Syck::DumpCode
These flags control whether or not to try and eval/deparse perl source code; each of them defaults to false.

Setting $YAML::Syck::UseCode to a true value is equivalent to setting both $YAML::Syck::LoadCode and $YAML::Syck::DumpCode to true.

  $YAML::Syck::LoadBlessed
Defaults to false. Setting to true will allow YAML::Syck to bless objects as it imports objects. This default changed in 1.32.

You can create any kind of object with YAML. The creation itself is not the critical part. If the class has a DESTROY method, it will be called once the object is deleted. An example with File::Temp removing files can be found at <https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=862373>

ENCODING-EXPLICIT FUNCTIONS
The standard "Load" and "Dump" functions rely on Perl's internal string representation, which can lead to surprising results when a string has been "utf8::upgrade"'d. The following functions make the encoding explicit:

  LoadBytes($yaml_string)
Treats the input as a byte (octet) string. If the string has been internally upgraded to UTF-8 by Perl, it is downgraded first so the parser sees the original bytes. Croaks if the string contains characters above 0xFF.

    use YAML::Syck qw(LoadBytes);
    my $data = LoadBytes($yaml_bytes);

  LoadUTF8($yaml_string)
Treats the input as UTF-8. The parsed values will have Perl's UTF-8 flag set (equivalent to "local $YAML::Syck::ImplicitUnicode = 1"). Works correctly regardless of whether the input string is upgraded or not.

    use YAML::Syck qw(LoadUTF8);
    my $data = LoadUTF8($yaml_utf8);

  DumpBytes($data, ...)
Dumps data to a YAML byte string. The return value will never have the UTF-8 flag set; any UTF-8 content is encoded to raw bytes.

    use YAML::Syck qw(DumpBytes);
    my $yaml = DumpBytes($data);

  DumpUTF8($data, ...)
Dumps data to a YAML string with the UTF-8 flag set (equivalent to "local $YAML::Syck::ImplicitUnicode = 1").

    use YAML::Syck qw(DumpUTF8);
    my $yaml = DumpUTF8($data);

BUGS
Dumping Glob/IO values do not work yet.

Dumping into tied (or other magic variables) with "DumpInto" might not work properly in all cases.

CAVEATS
This module implements the YAML 1.0 spec. To deal with data in YAML 1.1, please use the "YAML::XS" module instead.

The current implementation bundles libsyck source code; if your system has a site-wide shared libsyck, it will not be used.

Tag names such as "!!perl/hash:Foo" is blessed into the package "Foo", but the "!hs/foo" and "!!hs/Foo" tags are blessed into "hs::Foo". Note that this holds true even if the tag contains non-word characters; for example, "!haskell.org/Foo" is blessed into "haskell.org::Foo". Please use Class::Rebless to cast it into other user-defined packages. You can also set the LoadBlessed flag false to disable all blessing.

This module has a lot of known issues <https://rt.cpan.org/Public/Dist/Display.html?Name=YAML-Syck> and has only been semi-actively maintained since 2007. If you encounter an issue with it probably won't be fixed unless you offer up a patch <http://github.com/toddr/YAML-Syck> in Git that's ready for release.

There are still good reasons to use this module, such as better interoperability with other syck wrappers (like Ruby's), or some edge case of YAML's syntax that it handles better. It'll probably work perfectly for you, but if it doesn't you may want to look at YAML::XS, or perhaps at looking another serialization format like JSON.

SEE ALSO
YAML, JSON::Syck

<http://www.yaml.org/>

AUTHORS
Audrey Tang <cpan@audreyt.org>

COPYRIGHT
Copyright 2005-2009 by Audrey Tang <cpan@audreyt.org>.

This software is released under the MIT license cited below.

The libsyck code bundled with this library is released by "why the lucky stiff", under a BSD-style license. See the COPYING file for details.

  The "MIT" License
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.