Dump Ruby object o to a YAML string. Optional options may be passed in to control the output format. If an IO object is passed in, the YAML will be dumped to that IO object.

Currently supported options are:

:indentation

Number of space characters used to indent. Acceptable value should be in 0..9 range, otherwise option is ignored.

Default: 2.

:line_width

Max character to wrap line at.

Default: 0 (meaning “wrap at 81”).

:canonical

Write “canonical” YAML form (very verbose, yet strictly formal).

Default: false.

:header

Write %YAML [version] at the beginning of document.

Default: false.

Example:

# Dump an array, get back a YAML string
Psych.dump(['a', 'b'])  # => "---\n- a\n- b\n"

# Dump an array to an IO object
Psych.dump(['a', 'b'], StringIO.new)  # => #<StringIO:0x000001009d0890>

# Dump an array with indentation set
Psych.dump(['a', ['b']], indentation: 3) # => "---\n- a\n-  - b\n"

# Dump an array to an IO with indentation set
Psych.dump(['a', ['b']], StringIO.new, indentation: 3)

# File ext/psych/lib/psych.rb, line 505
def self.dump o, io = nil, options = {}
  if Hash === io
    options = io
    io      = nil
  end

  visitor = Psych::Visitors::YAMLTree.create options
  visitor << o
  visitor.tree.yaml io, options
end

Dump a list of objects as separate documents to a document stream.

Example:

Psych.dump_stream("foo\n  ", {}) # => "--- ! \"foo\\n  \"\n--- {}\n"

# File ext/psych/lib/psych.rb, line 595
def self.dump_stream *objects
  visitor = Psych::Visitors::YAMLTree.create({})
  objects.each do |o|
    visitor << o
  end
  visitor.tree.yaml
end

Returns the version of libyaml being used

static VALUE libyaml_version(VALUE module)
{
    int major, minor, patch;
    VALUE list[3];

    yaml_get_version(&major, &minor, &patch);

    list[0] = INT2NUM(major);
    list[1] = INT2NUM(minor);
    list[2] = INT2NUM(patch);

    return rb_ary_new4((long)3, list);
}

Load yaml in to a Ruby data structure. If multiple documents are provided, the object contained in the first document will be returned. filename will be used in the exception message if any exception is raised while parsing. If yaml is empty, it returns the specified fallback return value, which defaults to false.

Raises a Psych::SyntaxError when a YAML syntax error is detected.

Example:

Psych.load("--- a")             # => 'a'
Psych.load("---\n - a\n - b")   # => ['a', 'b']

begin
  Psych.load("--- `", filename: "file.txt")
rescue Psych::SyntaxError => ex
  ex.file    # => 'file.txt'
  ex.message # => "(file.txt): found character that cannot start any token"
end

When the optional symbolize_names keyword argument is set to a true value, returns symbols for keys in Hash objects (default: strings).

Psych.load("---\n foo: bar")                         # => {"foo"=>"bar"}
Psych.load("---\n foo: bar", symbolize_names: true)  # => {:foo=>"bar"}

Raises a TypeError when ‘yaml` parameter is NilClass. This method is similar to `safe_load` except that `Symbol` objects are allowed by default.

# File ext/psych/lib/psych.rb, line 368
def self.load yaml, permitted_classes: [Symbol], permitted_symbols: [], aliases: false, filename: nil, fallback: nil, symbolize_names: false, freeze: false, strict_integer: false
  safe_load yaml, permitted_classes: permitted_classes,
                  permitted_symbols: permitted_symbols,
                  aliases: aliases,
                  filename: filename,
                  fallback: fallback,
                  symbolize_names: symbolize_names,
                  freeze: freeze,
                  strict_integer: strict_integer
end

Loads the document contained in filename. Returns the yaml contained in filename as a Ruby object, or if the file is empty, it returns the specified fallback return value, which defaults to false. See load for options.

# File ext/psych/lib/psych.rb, line 669
def self.load_file filename, **kwargs
  File.open(filename, 'r:bom|utf-8') { |f|
    self.load f, filename: filename, **kwargs
  }
end

Load multiple documents given in yaml. Returns the parsed documents as a list. If a block is given, each document will be converted to Ruby and passed to the block during parsing

Example:

Psych.load_stream("--- foo\n...\n--- bar\n...") # => ['foo', 'bar']

list = []
Psych.load_stream("--- foo\n...\n--- bar\n...") do |ruby|
  list << ruby
end
list # => ['foo', 'bar']

# File ext/psych/lib/psych.rb, line 626
def self.load_stream yaml, filename: nil, fallback: [], **kwargs
  result = if block_given?
             parse_stream(yaml, filename: filename) do |node|
               yield node.to_ruby(**kwargs)
             end
           else
             parse_stream(yaml, filename: filename).children.map { |node| node.to_ruby(**kwargs) }
           end

  return fallback if result.is_a?(Array) && result.empty?
  result
end

Parse a YAML string in yaml. Returns the Psych::Nodes::Document. filename is used in the exception message if a Psych::SyntaxError is raised.

Raises a Psych::SyntaxError when a YAML syntax error is detected.

Example:

Psych.parse("---\n - a\n - b") # => #<Psych::Nodes::Document:0x00>

begin
  Psych.parse("--- `", filename: "file.txt")
rescue Psych::SyntaxError => ex
  ex.file    # => 'file.txt'
  ex.message # => "(file.txt): found character that cannot start any token"
end

See Psych::Nodes for more information about YAML AST.

# File ext/psych/lib/psych.rb, line 398
def self.parse yaml, filename: nil
  parse_stream(yaml, filename: filename) do |node|
    return node
  end

  false
end

Parse a file at filename. Returns the Psych::Nodes::Document.

Raises a Psych::SyntaxError when a YAML syntax error is detected.

# File ext/psych/lib/psych.rb, line 410
def self.parse_file filename, fallback: false
  result = File.open filename, 'r:bom|utf-8' do |f|
    parse f, filename: filename
  end
  result || fallback
end

Parse a YAML string in yaml. Returns the Psych::Nodes::Stream. This method can handle multiple YAML documents contained in yaml. filename is used in the exception message if a Psych::SyntaxError is raised.

If a block is given, a Psych::Nodes::Document node will be yielded to the block as it’s being parsed.

Raises a Psych::SyntaxError when a YAML syntax error is detected.

Example:

Psych.parse_stream("---\n - a\n - b") # => #<Psych::Nodes::Stream:0x00>

Psych.parse_stream("--- a\n--- b") do |node|
  node # => #<Psych::Nodes::Document:0x00>
end

begin
  Psych.parse_stream("--- `", filename: "file.txt")
rescue Psych::SyntaxError => ex
  ex.file    # => 'file.txt'
  ex.message # => "(file.txt): found character that cannot start any token"
end

Raises a TypeError when NilClass is passed.

See Psych::Nodes for more information about YAML AST.

# File ext/psych/lib/psych.rb, line 452
def self.parse_stream yaml, filename: nil, &block
  if block_given?
    parser = Psych::Parser.new(Handlers::DocumentStream.new(&block))
    parser.parse yaml, filename
  else
    parser = self.parser
    parser.parse yaml, filename
    parser.handler.root
  end
end

Returns a default parser

# File ext/psych/lib/psych.rb, line 419
def self.parser
  Psych::Parser.new(TreeBuilder.new)
end

Safely dump Ruby object o to a YAML string. Optional options may be passed in to control the output format. If an IO object is passed in, the YAML will be dumped to that IO object. By default, only the following classes are allowed to be serialized:

• TrueClass

• FalseClass

• NilClass

• Integer

• Float

• String

• Array

• Hash

Arbitrary classes can be allowed by adding those classes to the permitted_classes keyword argument. They are additive. For example, to allow Date serialization:

Psych.safe_dump(yaml, permitted_classes: [Date])

Now the Date class can be dumped in addition to the classes listed above.

A Psych::DisallowedClass exception will be raised if the object contains a class that isn’t in the permitted_classes list.

Currently supported options are:

:indentation

Number of space characters used to indent. Acceptable value should be in 0..9 range, otherwise option is ignored.

Default: 2.

:line_width

Max character to wrap line at.

Default: 0 (meaning “wrap at 81”).

:canonical

Write “canonical” YAML form (very verbose, yet strictly formal).

Default: false.

:header

Write %YAML [version] at the beginning of document.

Default: false.

Example:

# Dump an array, get back a YAML string
Psych.safe_dump(['a', 'b'])  # => "---\n- a\n- b\n"

# Dump an array to an IO object
Psych.safe_dump(['a', 'b'], StringIO.new)  # => #<StringIO:0x000001009d0890>

# Dump an array with indentation set
Psych.safe_dump(['a', ['b']], indentation: 3) # => "---\n- a\n-  - b\n"

# Dump an array to an IO with indentation set
Psych.safe_dump(['a', ['b']], StringIO.new, indentation: 3)

# File ext/psych/lib/psych.rb, line 578
def self.safe_dump o, io = nil, options = {}
  if Hash === io
    options = io
    io      = nil
  end

  visitor = Psych::Visitors::RestrictedYAMLTree.create options
  visitor << o
  visitor.tree.yaml io, options
end

Safely load the yaml string in yaml. By default, only the following classes are allowed to be deserialized:

• TrueClass

• FalseClass

• NilClass

• Integer

• Float

• String

• Array

• Hash

Recursive data structures are not allowed by default. Arbitrary classes can be allowed by adding those classes to the permitted_classes keyword argument. They are additive. For example, to allow Date deserialization:

Psych.safe_load(yaml, permitted_classes: [Date])

Now the Date class can be loaded in addition to the classes listed above.

Aliases can be explicitly allowed by changing the aliases keyword argument. For example:

x = []
x << x
yaml = Psych.dump x
Psych.safe_load yaml               # => raises an exception
Psych.safe_load yaml, aliases: true # => loads the aliases

A Psych::DisallowedClass exception will be raised if the yaml contains a class that isn’t in the permitted_classes list.

A Psych::BadAlias exception will be raised if the yaml contains aliases but the aliases keyword argument is set to false.

filename will be used in the exception message if any exception is raised while parsing.

When the optional symbolize_names keyword argument is set to a true value, returns symbols for keys in Hash objects (default: strings).

Psych.safe_load("---\n foo: bar")                         # => {"foo"=>"bar"}
Psych.safe_load("---\n foo: bar", symbolize_names: true)  # => {:foo=>"bar"}

# File ext/psych/lib/psych.rb, line 322
def self.safe_load yaml, permitted_classes: [], permitted_symbols: [], aliases: false, filename: nil, fallback: nil, symbolize_names: false, freeze: false, strict_integer: false
  result = parse(yaml, filename: filename)
  return fallback unless result

  class_loader = ClassLoader::Restricted.new(permitted_classes.map(&:to_s),
                                             permitted_symbols.map(&:to_s))
  scanner      = ScalarScanner.new class_loader, strict_integer: strict_integer
  visitor = if aliases
              Visitors::ToRuby.new scanner, class_loader, symbolize_names: symbolize_names, freeze: freeze
            else
              Visitors::NoAliasRuby.new scanner, class_loader, symbolize_names: symbolize_names, freeze: freeze
            end
  result = visitor.accept result
  result
end

Safely loads the document contained in filename. Returns the yaml contained in filename as a Ruby object, or if the file is empty, it returns the specified fallback return value, which defaults to false. See safe_load for options.

# File ext/psych/lib/psych.rb, line 658
def self.safe_load_file filename, **kwargs
  File.open(filename, 'r:bom|utf-8') { |f|
    self.safe_load f, filename: filename, **kwargs
  }
end

Dump Ruby object to a JSON string.

# File ext/psych/lib/psych.rb, line 605
def self.to_json object
  visitor = Psych::Visitors::JSONTree.create
  visitor << object
  visitor.tree.yaml
end

Load yaml in to a Ruby data structure. If multiple documents are provided, the object contained in the first document will be returned. filename will be used in the exception message if any exception is raised while parsing. If yaml is empty, it returns the specified fallback return value, which defaults to false.

Raises a Psych::SyntaxError when a YAML syntax error is detected.

Example:

Psych.unsafe_load("--- a")             # => 'a'
Psych.unsafe_load("---\n - a\n - b")   # => ['a', 'b']

begin
  Psych.unsafe_load("--- `", filename: "file.txt")
rescue Psych::SyntaxError => ex
  ex.file    # => 'file.txt'
  ex.message # => "(file.txt): found character that cannot start any token"
end

When the optional symbolize_names keyword argument is set to a true value, returns symbols for keys in Hash objects (default: strings).

Psych.unsafe_load("---\n foo: bar")                         # => {"foo"=>"bar"}
Psych.unsafe_load("---\n foo: bar", symbolize_names: true)  # => {:foo=>"bar"}

Raises a TypeError when ‘yaml` parameter is NilClass

NOTE: This method *should not* be used to parse untrusted documents, such as YAML documents that are supplied via user input. Instead, please use the load method or the safe_load method.

# File ext/psych/lib/psych.rb, line 271
def self.unsafe_load yaml, filename: nil, fallback: false, symbolize_names: false, freeze: false, strict_integer: false
  result = parse(yaml, filename: filename)
  return fallback unless result
  result.to_ruby(symbolize_names: symbolize_names, freeze: freeze, strict_integer: strict_integer)
end

Load the document contained in filename. Returns the yaml contained in filename as a Ruby object, or if the file is empty, it returns the specified fallback return value, which defaults to false.

NOTE: This method *should not* be used to parse untrusted documents, such as YAML documents that are supplied via user input. Instead, please use the safe_load_file method.

# File ext/psych/lib/psych.rb, line 647
def self.unsafe_load_file filename, **kwargs
  File.open(filename, 'r:bom|utf-8') { |f|
    self.unsafe_load f, filename: filename, **kwargs
  }
end