+++ /dev/null
-NAME
- YAML - YAML Ain't Markup Language (tm)
-
-SYNOPSIS
- use YAML;
-
- # Load a YAML stream of 3 YAML documents into Perl data structures.
- my ($hashref, $arrayref, $string) = Load(<<'...');
- ---
- name: ingy
- age: old
- weight: heavy
- # I should comment that I also like pink, but don't tell anybody.
- favorite colors:
- - red
- - green
- - blue
- ---
- - Clark Evans
- - Oren Ben-Kiki
- - Ingy döt Net
- --- >
- You probably think YAML stands for "Yet Another Markup Language". It
- ain't! YAML is really a data serialization language. But if you want
- to think of it as a markup, that's OK with me. A lot of people try
- to use XML as a serialization format.
-
- "YAML" is catchy and fun to say. Try it. "YAML, YAML, YAML!!!"
- ...
-
- # Dump the Perl data structures back into YAML.
- print Dump($string, $arrayref, $hashref);
-
- # YAML::Dump is used the same way you'd use Data::Dumper::Dumper
- use Data::Dumper;
- print Dumper($string, $arrayref, $hashref);
-
-DESCRIPTION
- The YAML.pm module implements a YAML Loader and Dumper based on the YAML
- 1.0 specification. <http://www.yaml.org/spec/>
-
- YAML is a generic data serialization language that is optimized for
- human readability. It can be used to express the data structures of most
- modern programming languages. (Including Perl!!!)
-
- For information on the YAML syntax, please refer to the YAML
- specification.
-
-WHY YAML IS COOL
- YAML is readable for people.
- It makes clear sense out of complex data structures. You should find
- that YAML is an exceptional data dumping tool. Structure is shown
- through indentation, YAML supports recursive data, and hash keys are
- sorted by default. In addition, YAML supports several styles of
- scalar formatting for different types of data.
-
- YAML is editable.
- YAML was designed from the ground up to be an excellent syntax for
- configuration files. Almost all programs need configuration files,
- so why invent a new syntax for each one? And why subject users to
- the complexities of XML or native Perl code?
-
- YAML is multilingual.
- Yes, YAML supports Unicode. But I'm actually referring to
- programming languages. YAML was designed to meet the serialization
- needs of Perl, Python, Ruby, Tcl, PHP, Javascript and Java. It was
- also designed to be interoperable between those languages. That
- means YAML serializations produced by Perl can be processed by
- Python.
-
- YAML is taint safe.
- Using modules like Data::Dumper for serialization is fine as long as
- you can be sure that nobody can tamper with your data files or
- transmissions. That's because you need to use Perl's "eval()"
- built-in to deserialize the data. Somebody could add a snippet of
- Perl to erase your files.
-
- YAML's parser does not need to eval anything.
-
- YAML is full featured.
- YAML can accurately serialize all of the common Perl data structures
- and deserialize them again without losing data relationships.
- Although it is not 100% perfect (no serializer is or can be
- perfect), it fares as well as the popular current modules:
- Data::Dumper, Storable, XML::Dumper and Data::Denter.
-
- YAML.pm also has the ability to handle code (subroutine) references
- and typeglobs. (Still experimental) These features are not found in
- Perl's other serialization modules.
-
- YAML is extensible.
- The YAML language has been designed to be flexible enough to solve
- it's own problems. The markup itself has 3 basic construct which
- resemble Perl's hash, array and scalar. By default, these map to
- their Perl equivalents. But each YAML node also supports a tagging
- mechanism (type system) which can cause that node to be interpreted
- in a completely different manner. That's how YAML can support object
- serialization and oddball structures like Perl's typeglob.
-
-YAML IMPLEMENTATIONS IN PERL
- This module, YAML.pm, is really just the interface module for YAML
- modules written in Perl. The basic interface for YAML consists of two
- functions: "Dump" and "Load". The real work is done by the modules
- YAML::Dumper and YAML::Loader.
-
- Different YAML module distributions can be created by subclassing
- YAML.pm and YAML::Loader and YAML::Dumper. For example, YAML-Simple
- consists of YAML::Simple YAML::Dumper::Simple and YAML::Loader::Simple.
-
- Why would there be more than one implementation of YAML? Well, despite
- YAML's offering of being a simple data format, YAML is actually very
- deep and complex. Implementing the entirety of the YAML specification is
- a daunting task.
-
- For this reason I am currently working on 3 different YAML
- implementations.
-
- YAML
- The main YAML distribution will keeping evolving to support the
- entire YAML specification in pure Perl. This may not be the fastest
- or most stable module though. Currently, YAML.pm has lots of known
- bugs. It is mostly a great tool for dumping Perl data structures to
- a readable form.
-
- YAML::Lite
- The point of YAML::Lite is to strip YAML down to the 90% that people
- use most and offer that in a small, fast, stable, pure Perl form.
- YAML::Lite will simply die when it is asked to do something it
- can't.
-
- YAML::Syck
- "libsyck" is the C based YAML processing library used by the Ruby
- programming language (and also Python, PHP and Pugs). YAML::Syck is
- the Perl binding to "libsyck". It should be very fast, but may have
- problems of its own. It will also require C compilation.
-
- NOTE: Audrey Tang has actually completed this module and it works
- great and is 10 times faster than YAML.pm.
-
- In the future, there will likely be even more YAML modules. Remember,
- people other than Ingy are allowed to write YAML modules!
-
-FUNCTIONAL USAGE
- YAML is completely OO under the hood. Still it exports a few useful top
- level functions so that it is dead simple to use. These functions just
- do the OO stuff for you. If you want direct access to the OO API see the
- documentation for YAML::Dumper and YAML::Loader.
-
- Exported Functions
- The following functions are exported by YAML.pm by default. The reason
- they are exported is so that YAML works much like Data::Dumper. If you
- don't want functions to be imported, just use YAML with an empty import
- list:
-
- use YAML ();
-
- 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 strucures and
- dumps them into a serialized form. It returns a string containing
- the YAML stream. The structures can be references or plain scalars.
-
- 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 string containing a valid YAML stream into
- a list of Perl data structures.
-
- Exportable Functions
- These functions are not exported by default but you can request them in
- an import list like this:
-
- use YAML qw'freeze thaw Bless';
-
- freeze() and thaw()
- Aliases to Dump() and Load() for Storable fans. This will also allow
- YAML.pm 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 instead of just returning a string.
-
- LoadFile(filepath)
- Reads the YAML stream from a file instead of a string.
-
- Bless(perl-node, [yaml-node | class-name])
- Associate a normal Perl node, with a yaml node. A yaml node is an
- object tied to the YAML::Node class. The second argument is either a
- yaml node that you've already created or a class (package) name that
- supports a yaml_dump() function. A yaml_dump() function should take
- a perl node and return a yaml node. If no second argument is
- provided, Bless will create a yaml node. This node is not returned,
- but can be retrieved with the Blessed() function.
-
- Here's an example of how to use Bless. Say you have a hash
- containing three keys, but you only want to dump two of them.
- Furthermore the keys must be dumped in a certain order. Here's how
- you do that:
-
- use YAML qw(Dump Bless);
- $hash = {apple => 'good', banana => 'bad', cauliflower => 'ugly'};
- print Dump $hash;
- Bless($hash)->keys(['banana', 'apple']);
- print Dump $hash;
-
- produces:
-
- ---
- apple: good
- banana: bad
- cauliflower: ugly
- ---
- banana: bad
- apple: good
-
- Bless returns the tied part of a yaml-node, so that you can call the
- YAML::Node methods. This is the same thing that YAML::Node::ynode()
- returns. So another way to do the above example is:
-
- use YAML qw(Dump Bless);
- use YAML::Node;
- $hash = {apple => 'good', banana => 'bad', cauliflower => 'ugly'};
- print Dump $hash;
- Bless($hash);
- $ynode = ynode(Blessed($hash));
- $ynode->keys(['banana', 'apple']);
- print Dump $hash;
-
- Note that Blessing a Perl data structure does not change it anyway.
- The extra information is stored separately and looked up by the
- Blessed node's memory address.
-
- Blessed(perl-node)
- Returns the yaml node that a particular perl node is associated with
- (see above). Returns undef if the node is not (YAML) Blessed.
-
-GLOBAL OPTIONS
- YAML options are set using a group of global variables in the YAML
- namespace. This is similar to how Data::Dumper works.
-
- For example, to change the indentation width, do something like:
-
- local $YAML::Indent = 3;
-
- The current options are:
-
- DumperClass
- You can override which module/class YAML uses for Dumping data.
-
- LoaderClass
- You can override which module/class YAML uses for Loading data.
-
- Indent
- This is the number of space characters to use for each indentation
- level when doing a Dump(). The default is 2.
-
- By the way, YAML can use any number of characters for indentation at
- any level. So if you are editing YAML by hand feel free to do it
- anyway that looks pleasing to you; just be consistent for a given
- level.
-
- SortKeys
- Default is 1. (true)
-
- Tells YAML.pm whether or not to sort hash keys when storing a
- document.
-
- YAML::Node objects can have their own sort order, which is usually
- what you want. To override the YAML::Node order and sort the keys
- anyway, set SortKeys to 2.
-
- Stringify
- Default is 0. (false)
-
- Objects with string overloading should honor the overloading and
- dump the stringification of themselves, rather than the actual
- object's guts.
-
- UseHeader
- Default is 1. (true)
-
- This tells YAML.pm whether to use a separator string for a Dump
- operation. This only applies to the first document in a stream.
- Subsequent documents must have a YAML header by definition.
-
- UseVersion
- Default is 0. (false)
-
- Tells YAML.pm whether to include the YAML version on the
- separator/header.
-
- --- %YAML:1.0
-
- AnchorPrefix
- Default is ''.
-
- Anchor names are normally numeric. YAML.pm simply starts with '1'
- and increases by one for each new anchor. This option allows you to
- specify a string to be prepended to each anchor number.
-
- UseCode
- Setting the UseCode option is a shortcut to set both the DumpCode
- and LoadCode options at once. Setting UseCode to '1' tells YAML.pm
- to dump Perl code references as Perl (using B::Deparse) and to load
- them back into memory using eval(). The reason this has to be an
- option is that using eval() to parse untrusted code is, well,
- untrustworthy.
-
- DumpCode
- Determines if and how YAML.pm should serialize Perl code references.
- By default YAML.pm will dump code references as dummy placeholders
- (much like Data::Dumper). If DumpCode is set to '1' or 'deparse',
- code references will be dumped as actual Perl code.
-
- DumpCode can also be set to a subroutine reference so that you can
- write your own serializing routine. YAML.pm passes you the code ref.
- You pass back the serialization (as a string) and a format
- indicator. The format indicator is a simple string like: 'deparse'
- or 'bytecode'.
-
- LoadCode
- LoadCode is the opposite of DumpCode. It tells YAML if and how to
- deserialize code references. When set to '1' or 'deparse' it will
- use "eval()". Since this is potentially risky, only use this option
- if you know where your YAML has been.
-
- LoadCode can also be set to a subroutine reference so that you can
- write your own deserializing routine. YAML.pm passes the
- serialization (as a string) and a format indicator. You pass back
- the code reference.
-
- UseBlock
- YAML.pm uses heuristics to guess which scalar style is best for a
- given node. Sometimes you'll want all multiline scalars to use the
- 'block' style. If so, set this option to 1.
-
- NOTE: YAML's block style is akin to Perl's here-document.
-
- UseFold
- If you want to force YAML to use the 'folded' style for all
- multiline scalars, then set $UseFold to 1.
-
- NOTE: YAML's folded style is akin to the way HTML folds text, except
- smarter.
-
- UseAliases
- YAML has an alias mechanism such that any given structure in memory
- gets serialized once. Any other references to that structure are
- serialized only as alias markers. This is how YAML can serialize
- duplicate and recursive structures.
-
- Sometimes, when you KNOW that your data is nonrecursive in nature,
- you may want to serialize such that every node is expressed in full.
- (ie as a copy of the original). Setting $YAML::UseAliases to 0 will
- allow you to do this. This also may result in faster processing
- because the lookup overhead is by bypassed.
-
- THIS OPTION CAN BE DANGEROUS. *If* your data is recursive, this
- option *will* cause Dump() to run in an endless loop, chewing up
- your computers memory. You have been warned.
-
- CompressSeries
- Default is 1.
-
- Compresses the formatting of arrays of hashes:
-
- -
- foo: bar
- -
- bar: foo
-
- becomes:
-
- - foo: bar
- - bar: foo
-
- Since this output is usually more desirable, this option is turned
- on by default.
-
-YAML TERMINOLOGY
- YAML is a full featured data serialization language, and thus has its
- own terminology.
-
- It is important to remember that although YAML is heavily influenced by
- Perl and Python, it is a language in its own right, not merely just a
- representation of Perl structures.
-
- YAML has three constructs that are conspicuously similar to Perl's hash,
- array, and scalar. They are called mapping, sequence, and string
- respectively. By default, they do what you would expect. But each
- instance may have an explicit or implicit tag (type) that makes it
- behave differently. In this manner, YAML can be extended to represent
- Perl's Glob or Python's tuple, or Ruby's Bigint.
-
- stream
- A YAML stream is the full sequence of unicode characters that a YAML
- parser would read or a YAML emitter would write. A stream may
- contain one or more YAML documents separated by YAML headers.
-
- ---
- a: mapping
- foo: bar
- ---
- - a
- - sequence
-
- document
- A YAML document is an independent data structure representation
- within a stream. It is a top level node. Each document in a YAML
- stream must begin with a YAML header line. Actually the header is
- optional on the first document.
-
- ---
- This: top level mapping
- is:
- - a
- - YAML
- - document
-
- header
- A YAML header is a line that begins a YAML document. It consists of
- three dashes, possibly followed by more info. Another purpose of the
- header line is that it serves as a place to put top level tag and
- anchor information.
-
- --- !recursive-sequence &001
- - * 001
- - * 001
-
- node
- A YAML node is the representation of a particular data stucture.
- Nodes may contain other nodes. (In Perl terms, nodes are like
- scalars. Strings, arrayrefs and hashrefs. But this refers to the
- serialized format, not the in-memory structure.)
-
- tag This is similar to a type. It indicates how a particular YAML node
- serialization should be transferred into or out of memory. For
- instance a Foo::Bar object would use the tag 'perl/Foo::Bar':
-
- - !perl/Foo::Bar
- foo: 42
- bar: stool
-
- collection
- A collection is the generic term for a YAML data grouping. YAML has
- two types of collections: mappings and sequences. (Similar to hashes
- and arrays)
-
- mapping
- A mapping is a YAML collection defined by unordered key/value pairs
- with unique keys. By default YAML mappings are loaded into Perl
- hashes.
-
- a mapping:
- foo: bar
- two: times two is 4
-
- sequence
- A sequence is a YAML collection defined by an ordered list of
- elements. By default YAML sequences are loaded into Perl arrays.
-
- a sequence:
- - one bourbon
- - one scotch
- - one beer
-
- scalar
- A scalar is a YAML node that is a single value. By default YAML
- scalars are loaded into Perl scalars.
-
- a scalar key: a scalar value
-
- YAML has many styles for representing scalars. This is important
- because varying data will have varying formatting requirements to
- retain the optimum human readability.
-
- plain scalar
- A plain sclar is unquoted. All plain scalars are automatic
- candidates for "implicit tagging". This means that their tag may be
- determined automatically by examination. The typical uses for this
- are plain alpha strings, integers, real numbers, dates, times and
- currency.
-
- - a plain string
- - -42
- - 3.1415
- - 12:34
- - 123 this is an error
-
- single quoted scalar
- This is similar to Perl's use of single quotes. It means no escaping
- except for single quotes which are escaped by using two adjacent
- single quotes.
-
- - 'When I say ''\n'' I mean "backslash en"'
-
- double quoted scalar
- This is similar to Perl's use of double quotes. Character escaping
- can be used.
-
- - "This scalar\nhas two lines, and a bell -->\a"
-
- folded scalar
- This is a multiline scalar which begins on the next line. It is
- indicated by a single right angle bracket. It is unescaped like the
- single quoted scalar. Line folding is also performed.
-
- - >
- This is a multiline scalar which begins on
- the next line. It is indicated by a single
- carat. It is unescaped like the single
- quoted scalar. Line folding is also
- performed.
-
- block scalar
- This final multiline form is akin to Perl's here-document except
- that (as in all YAML data) scope is indicated by indentation.
- Therefore, no ending marker is required. The data is verbatim. No
- line folding.
-
- - |
- QTY DESC PRICE TOTAL
- --- ---- ----- -----
- 1 Foo Fighters $19.95 $19.95
- 2 Bar Belles $29.95 $59.90
-
- parser
- A YAML processor has four stages: parse, load, dump, emit.
-
- A parser parses a YAML stream. YAML.pm's Load() function contains a
- parser.
-
- loader
- The other half of the Load() function is a loader. This takes the
- information from the parser and loads it into a Perl data structure.
-
- dumper
- The Dump() function consists of a dumper and an emitter. The dumper
- walks through each Perl data structure and gives info to the
- emitter.
-
- emitter
- The emitter takes info from the dumper and turns it into a YAML
- stream.
-
- NOTE: In YAML.pm the parser/loader and the dumper/emitter code are
- currently very closely tied together. In the future they may be
- broken into separate stages.
-
- For more information please refer to the immensely helpful YAML
- specification available at <http://www.yaml.org/spec/>.
-
-ysh - The YAML Shell
- The YAML distribution ships with a script called 'ysh', the YAML shell.
- ysh provides a simple, interactive way to play with YAML. If you type in
- Perl code, it displays the result in YAML. If you type in YAML it turns
- it into Perl code.
-
- To run ysh, (assuming you installed it along with YAML.pm) simply type:
-
- ysh [options]
-
- Please read the "ysh" documentation for the full details. There are lots
- of options.
-
-BUGS & DEFICIENCIES
- If you find a bug in YAML, please try to recreate it in the YAML Shell
- with logging turned on ('ysh -L'). When you have successfully reproduced
- the bug, please mail the LOG file to the author (ingy@cpan.org).
-
- WARNING: This is still *ALPHA* code. Well, most of this code has been
- around for years...
-
- BIGGER WARNING: YAML.pm has been slow in the making, but I am committed
- to having top notch YAML tools in the Perl world. The YAML team is close
- to finalizing the YAML 1.1 spec. This version of YAML.pm is based off of
- a very old pre 1.0 spec. In actuality there isn't a ton of difference,
- and this YAML.pm is still fairly useful. Things will get much better in
- the future.
-
-RESOURCES
- <http://lists.sourceforge.net/lists/listinfo/yaml-core> is the mailing
- list. This is where the language is discussed and designed.
-
- <http://www.yaml.org> is the official YAML website.
-
- <http://www.yaml.org/spec/> is the YAML 1.0 specification.
-
- <http://yaml.kwiki.org> is the official YAML wiki.
-
-SEE ALSO
- See YAML::Syck. Fast!
-
-AUTHOR
- Ingy döt Net <ingy@cpan.org>
-
- is resonsible for YAML.pm.
-
- The YAML serialization language is the result of years of collaboration
- between Oren Ben-Kiki, Clark Evans and Ingy döt Net. Several others
- have added help along the way.
-
-COPYRIGHT
- Copyright (c) 2005, 2006. Ingy döt Net. All rights reserved. Copyright
- (c) 2001, 2002, 2005. Brian Ingerson. All rights reserved.
-
- This program is free software; you can redistribute it and/or modify it
- under the same terms as Perl itself.
-
- See <http://www.perl.com/perl/misc/Artistic.html>
-
projects / kivitendo-erp.git / blobdiff