Provided by: libyaml-tiny-perl_1.74-1_all 
NAME
YAML::Tiny - Read/Write YAML files with as little code as possible
VERSION
version 1.74
PREAMBLE
The YAML specification is huge. Really, really huge. It contains all the functionality of
XML, except with flexibility and choice, which makes it easier to read, but with a formal
specification that is more complex than XML.
The original pure-Perl implementation YAML costs just over 4 megabytes of memory to load.
Just like with Windows .ini files (3 meg to load) and CSS (3.5 meg to load) the situation
is just asking for a YAML::Tiny module, an incomplete but correct and usable subset of the
functionality, in as little code as possible.
Like the other "::Tiny" modules, YAML::Tiny has no non-core dependencies, does not require
a compiler to install, is back-compatible to Perl v5.8.1, and can be inlined into other
modules if needed.
In exchange for adding this extreme flexibility, it provides support for only a limited
subset of YAML. But the subset supported contains most of the features for the more common
uses of YAML.
SYNOPSIS
Assuming file.yml like this:
---
rootproperty: blah
section:
one: two
three: four
Foo: Bar
empty: ~
Read and write file.yml like this:
use YAML::Tiny;
# Open the config
my $yaml = YAML::Tiny->read( 'file.yml' );
# Get a reference to the first document
my $config = $yaml->[0];
# Or read properties directly
my $root = $yaml->[0]->{rootproperty};
my $one = $yaml->[0]->{section}->{one};
my $Foo = $yaml->[0]->{section}->{Foo};
# Change data directly
$yaml->[0]->{newsection} = { this => 'that' }; # Add a section
$yaml->[0]->{section}->{Foo} = 'Not Bar!'; # Change a value
delete $yaml->[0]->{section}; # Delete a value
# Save the document back to the file
$yaml->write( 'file.yml' );
To create a new YAML file from scratch:
# Create a new object with a single hashref document
my $yaml = YAML::Tiny->new( { wibble => "wobble" } );
# Add an arrayref document
push @$yaml, [ 'foo', 'bar', 'baz' ];
# Save both documents to a file
$yaml->write( 'data.yml' );
Then data.yml will contain:
---
wibble: wobble
---
- foo
- bar
- baz
DESCRIPTION
YAML::Tiny is a perl class for reading and writing YAML-style files, written with as
little code as possible, reducing load time and memory overhead.
Most of the time it is accepted that Perl applications use a lot of memory and modules.
The ::Tiny family of modules is specifically intended to provide an ultralight and zero-
dependency alternative to many more-thorough standard modules.
This module is primarily for reading human-written files (like simple config files) and
generating very simple human-readable files. Note that I said human-readable and not geek-
readable. The sort of files that your average manager or secretary should be able to look
at and make sense of.
YAML::Tiny does not generate comments, it won't necessarily preserve the order of your
hashes, and it will normalise if reading in and writing out again.
It only supports a very basic subset of the full YAML specification.
Usage is targeted at files like Perl's META.yml, for which a small and easily-embeddable
module is extremely attractive.
Features will only be added if they are human readable, and can be written in a few lines
of code. Please don't be offended if your request is refused. Someone has to draw the
line, and for YAML::Tiny that someone is me.
If you need something with more power move up to YAML (7 megabytes of memory overhead) or
YAML::XS (6 megabytes memory overhead and requires a C compiler).
To restate, YAML::Tiny does not preserve your comments, whitespace, or the order of your
YAML data. But it should round-trip from Perl structure to file and back again just fine.
METHODS
new
The constructor "new" creates a "YAML::Tiny" object as a blessed array reference. Any
arguments provided are taken as separate documents to be serialized.
read $filename
The "read" constructor reads a YAML file from a file name, and returns a new "YAML::Tiny"
object containing the parsed content.
Returns the object on success or throws an error on failure.
read_string $string;
The "read_string" constructor reads YAML data from a character string, and returns a new
"YAML::Tiny" object containing the parsed content. If you have read the string from a
file yourself, be sure that you have correctly decoded it into characters first.
Returns the object on success or throws an error on failure.
write $filename
The "write" method generates the file content for the properties, and writes it to disk
using UTF-8 encoding to the filename specified.
Returns true on success or throws an error on failure.
write_string
Generates the file content for the object and returns it as a character string. This may
contain non-ASCII characters and should be encoded before writing it to a file.
Returns true on success or throws an error on failure.
errstr (DEPRECATED)
Prior to version 1.57, some errors were fatal and others were available only via the
$YAML::Tiny::errstr variable, which could be accessed via the "errstr()" method.
Starting with version 1.57, all errors are fatal and throw exceptions.
The $errstr variable is still set when exceptions are thrown, but $errstr and the
"errstr()" method are deprecated and may be removed in a future release. The first use of
"errstr()" will issue a deprecation warning.
FUNCTIONS
YAML::Tiny implements a number of functions to add compatibility with the YAML API. These
should be a drop-in replacement.
Dump
my $string = Dump(list-of-Perl-data-structures);
Turn Perl data into YAML. This function works very much like Data::Dumper::Dumper().
It takes a list of Perl data structures and dumps them into a serialized form.
It returns a character string containing the YAML stream. Be sure to encode it as UTF-8
before serializing to a file or socket.
The structures can be references or plain scalars.
Dies on any error.
Load
my @data_structures = Load(string-containing-a-YAML-stream);
Turn YAML into Perl data. This is the opposite of Dump.
Just like Storable's thaw() function or the eval() function in relation to Data::Dumper.
It parses a character string containing a valid YAML stream into a list of Perl data
structures representing the individual YAML documents. Be sure to decode the character
string correctly if the string came from a file or socket.
my $last_data_structure = Load(string-containing-a-YAML-stream);
For consistency with YAML.pm, when Load is called in scalar context, it returns the data
structure corresponding to the last of the YAML documents found in the input stream.
Dies on any error.
freeze() and thaw()
Aliases to Dump() and Load() for Storable fans. This will also allow YAML::Tiny to be
plugged directly into modules like POE.pm, that use the freeze/thaw API for internal
serialization.
DumpFile(filepath, list)
Writes the YAML stream to a file with UTF-8 encoding instead of just returning a string.
Dies on any error.
LoadFile(filepath)
Reads the YAML stream from a UTF-8 encoded file instead of a string.
Dies on any error.
YAML TINY SPECIFICATION
This section of the documentation provides a specification for "YAML Tiny", a subset of
the YAML specification.
It is based on and described comparatively to the YAML 1.1 Working Draft 2004-12-28
specification, located at <http://yaml.org/spec/current.html>.
Terminology and chapter numbers are based on that specification.
1. Introduction and Goals
The purpose of the YAML Tiny specification is to describe a useful subset of the YAML
specification that can be used for typical document-oriented use cases such as
configuration files and simple data structure dumps.
Many specification elements that add flexibility or extensibility are intentionally
removed, as is support for complex data structures, class and object-orientation.
In general, the YAML Tiny language targets only those data structures available in JSON,
with the additional limitation that only simple keys are supported.
As a result, all possible YAML Tiny documents should be able to be transformed into an
equivalent JSON document, although the reverse is not necessarily true (but will be true
in simple cases).
As a result of these simplifications the YAML Tiny specification should be implementable
in a (relatively) small amount of code in any language that supports Perl Compatible
Regular Expressions (PCRE).
2. Introduction
YAML Tiny supports three data structures. These are scalars (in a variety of forms),
block-form sequences and block-form mappings. Flow-style sequences and mappings are not
supported, with some minor exceptions detailed later.
The use of three dashes "---" to indicate the start of a new document is supported, and
multiple documents per file/stream is allowed.
Both line and inline comments are supported.
Scalars are supported via the plain style, single quote and double quote, as well as
literal-style and folded-style multi-line scalars.
The use of explicit tags is not supported.
The use of "null" type scalars is supported via the ~ character.
The use of "bool" type scalars is not supported.
However, serializer implementations should take care to explicitly escape strings that
match a "bool" keyword in the following set to prevent other implementations that do
support "bool" accidentally reading a string as a boolean
y|Y|yes|Yes|YES|n|N|no|No|NO
|true|True|TRUE|false|False|FALSE
|on|On|ON|off|Off|OFF
The use of anchors and aliases is not supported.
The use of directives is supported only for the %YAML directive.
3. Processing YAML Tiny Information
Processes
The YAML specification dictates three-phase serialization and three-phase deserialization.
The YAML Tiny specification does not mandate any particular methodology or mechanism for
parsing.
Any compliant parser is only required to parse a single document at a time. The ability to
support streaming documents is optional and most likely non-typical.
Because anchors and aliases are not supported, the resulting representation graph is thus
directed but (unlike the main YAML specification) acyclic.
Circular references/pointers are not possible, and any YAML Tiny serializer detecting a
circular reference should error with an appropriate message.
Presentation Stream
YAML Tiny reads and write UTF-8 encoded files. Operations on strings expect or produce
Unicode characters not UTF-8 encoded bytes.
Loading Failure Points
YAML Tiny parsers and emitters are not expected to recover from, or adapt to, errors. The
specific error modality of any implementation is not dictated (return codes, exceptions,
etc.) but is expected to be consistent.
4. Syntax
Character Set
YAML Tiny streams are processed in memory as Unicode characters and read/written with
UTF-8 encoding.
The escaping and unescaping of the 8-bit YAML escapes is required.
The escaping and unescaping of 16-bit and 32-bit YAML escapes is not required.
Indicator Characters
Support for the "~" null/undefined indicator is required.
Implementations may represent this as appropriate for the underlying language.
Support for the "-" block sequence indicator is required.
Support for the "?" mapping key indicator is not required.
Support for the ":" mapping value indicator is required.
Support for the "," flow collection indicator is not required.
Support for the "[" flow sequence indicator is not required, with one exception (detailed
below).
Support for the "]" flow sequence indicator is not required, with one exception (detailed
below).
Support for the "{" flow mapping indicator is not required, with one exception (detailed
below).
Support for the "}" flow mapping indicator is not required, with one exception (detailed
below).
Support for the "#" comment indicator is required.
Support for the "&" anchor indicator is not required.
Support for the "*" alias indicator is not required.
Support for the "!" tag indicator is not required.
Support for the "|" literal block indicator is required.
Support for the ">" folded block indicator is required.
Support for the "'" single quote indicator is required.
Support for the """ double quote indicator is required.
Support for the "%" directive indicator is required, but only for the special case of a
%YAML version directive before the "---" document header, or on the same line as the
document header.
For example:
%YAML 1.1
---
- A sequence with a single element
Special Exception:
To provide the ability to support empty sequences and mappings, support for the constructs
[] (empty sequence) and {} (empty mapping) are required.
For example,
%YAML 1.1
# A document consisting of only an empty mapping
--- {}
# A document consisting of only an empty sequence
--- []
# A document consisting of an empty mapping within a sequence
- foo
- {}
- bar
Syntax Primitives
Other than the empty sequence and mapping cases described above, YAML Tiny supports only
the indentation-based block-style group of contexts.
All five scalar contexts are supported.
Indentation spaces work as per the YAML specification in all cases.
Comments work as per the YAML specification in all simple cases. Support for indented
multi-line comments is not required.
Separation spaces work as per the YAML specification in all cases.
YAML Tiny Character Stream
The only directive supported by the YAML Tiny specification is the %YAML language/version
identifier. Although detected, this directive will have no control over the parsing
itself.
The parser must recognise both the YAML 1.0 and YAML 1.1+ formatting of this directive (as
well as the commented form, although no explicit code should be needed to deal with this
case, being a comment anyway)
That is, all of the following should be supported.
--- #YAML:1.0
- foo
%YAML:1.0
---
- foo
% YAML 1.1
---
- foo
Support for the %TAG directive is not required.
Support for additional directives is not required.
Support for the document boundary marker "---" is required.
Support for the document boundary market "..." is not required.
If necessary, a document boundary should simply be indicated with a "---" marker, with no
preceding "..." marker.
Support for empty streams (containing no documents) is required.
Support for implicit document starts is required.
That is, the following must be equivalent.
# Full form
%YAML 1.1
---
foo: bar
# Implicit form
foo: bar
Nodes
Support for nodes optional anchor and tag properties is not required.
Support for node anchors is not required.
Support for node tags is not required.
Support for alias nodes is not required.
Support for flow nodes is not required.
Support for block nodes is required.
Scalar Styles
Support for all five scalar styles is required as per the YAML specification, although
support for quoted scalars spanning more than one line is not required.
Support for multi-line scalar documents starting on the header is not required.
Support for the chomping indicators on multi-line scalar styles is required.
Collection Styles
Support for block-style sequences is required.
Support for flow-style sequences is not required.
Support for block-style mappings is required.
Support for flow-style mappings is not required.
Both sequences and mappings should be able to be arbitrarily nested.
Support for plain-style mapping keys is required.
Support for quoted keys in mappings is not required.
Support for "?"-indicated explicit keys is not required.
Here endeth the specification.
Additional Perl-Specific Notes
For some Perl applications, it's important to know if you really have a number and not a
string.
That is, in some contexts is important that 3 the number is distinctive from "3" the
string.
Because even Perl itself is not trivially able to understand the difference (certainly
without XS-based modules) Perl implementations of the YAML Tiny specification are not
required to retain the distinctiveness of 3 vs "3".
SUPPORT
Bugs should be reported via the CPAN bug tracker at
<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=YAML-Tiny>
AUTHOR
Adam Kennedy <adamk@cpan.org>
SEE ALSO
• YAML
• YAML::Syck
• Config::Tiny
• CSS::Tiny
• <http://use.perl.org/use.perl.org/_Alias/journal/29427.html>
• <http://ali.as/>
COPYRIGHT
Copyright 2006 - 2013 Adam Kennedy.
This program is free software; you can redistribute it and/or modify it under the same
terms as Perl itself.
The full text of the license can be found in the LICENSE file included with this module.