MARC::Spec

A implementation of the MARCspec query language for Ruby and ruby-marc.

Usage

Add ruby-marc-spec to your Gemfile or gemspec, or just install it:

• Gemfile:

  gem 'ruby-marc-spec'

• gemspec

  spec.add_dependency 'ruby-marc-spec'

• from the command line:

  gem install ruby-marc-spec

Then, in your code:

require 'marc/spec'

The entry point for MARC::Spec is the MARC::Spec#find method, which takes a string MARCspec query and a MARC::Record object.

MARC::Spec.find('245$a', marc_record)
# => [#<MARC::Subfield:0x00007ffa1686e3f0 @code="a", @value="Arithmetic /">] 

Note that for simplicity's sake MARC::Spec#find always returns an array, even for queries that can only return a single-element result, e.g.

MARC::Spec.find('LDR', marc_record)
# => ["01142cam  2200301 a 4500"]

Examples

All examples below are based on the record sandburg.xml from the Library of Congress MARCXML documentation.

marc_record = MARC::XMLReader.new('sandburg.xml').first

Retrieving the leader

MARC::Spec.find('LDR', marc_record)
# => ["01142cam  2200301 a 4500"]

Retrieving control fields

Find all fields whose tag begins with 00:

MARC::Spec.find('00.', marc_record)
# => [
#  #<MARC::ControlField:0x00007ff9f706ac40 @tag="001", @value="   92005291 ">,
#  #<MARC::ControlField:0x00007ff9f70686c0 @tag="003", @value="DLC">,
#  #<MARC::ControlField:0x00007ff9f7062450 @tag="005", @value="19930521155141.9">,
#  #<MARC::ControlField:0x00007ff9f70600d8 @tag="008", @value="920219s1993    caua   j      000 0 eng  ">
# ]

Retrieving substrings of a control field value:

Find the first six characters (characters 0 through 6) of the 008 field:

MARC::Spec.find('008/0-5', marc_record)
# => ["920219"]

Retrieving data fields

Find the first two 650 fields (fields 0 and 1):

MARC::Spec.find('650[0-1]', marc_record)
# => [#<MARC::DataField:0x00007ffa1799a5c0
#   @indicator1=" ",
#   @indicator2="0",
#   @subfields=[#<MARC::Subfield:0x00007ffa17999878 @code="a", @value="Arithmetic">, #<MARC::Subfield:0x00007ffa179984a0 @code="x", @value="Juvenile poetry.">],
#   @tag="650">,
#  #<MARC::DataField:0x00007ffa17992618
#   @indicator1=" ",
#   @indicator2="0",
#   @subfields=[#<MARC::Subfield:0x00007ffa179918d0 @code="a", @value="Children's poetry, American.">],
#   @tag="650">] 

Retrieving subfields

Find subfield a of all 650 fields:

MARC::Spec.find('650$a', marc_record)
#  => 
# [#<MARC::Subfield:0x00007ffa17999878 @code="a", @value="Arithmetic">,
#  #<MARC::Subfield:0x00007ffa179918d0 @code="a", @value="Children's poetry, American.">,
#  #<MARC::Subfield:0x00007ffa1798acb0 @code="a", @value="Arithmetic">,
#  #<MARC::Subfield:0x00007ffa17982cb8 @code="a", @value="American poetry.">,
#  #<MARC::Subfield:0x00007ffa17980120 @code="a", @value="Visual perception.">]

Retrieving subfield values

Find the first six characters (characters 0 through 5) of subfield a of the fifth (zero-indexed) 650 field:

MARC::Spec.find('650[4]$a/0-5', marc_record)
# => ["Visual"]

Limiting results based on conditions:

Find all 650 fields having a value of 0 for the second indicator:

MARC::Spec.find('650{^2=\0}', marc_record)
# => 
# [#<MARC::DataField:0x00007ffa1799a5c0
#   @indicator1=" ",
#   @indicator2="0",
#   @subfields=[#<MARC::Subfield:0x00007ffa17999878 @code="a", @value="Arithmetic">, #<MARC::Subfield:0x00007ffa179984a0 @code="x", @value="Juvenile poetry.">],
#   @tag="650">,
#  #<MARC::DataField:0x00007ffa17992618
#   @indicator1=" ",
#   @indicator2="0",
#   @subfields=[#<MARC::Subfield:0x00007ffa179918d0 @code="a", @value="Children's poetry, American.">],
#   @tag="650">] 

Find subfield a of each 650 field that also has a subfield x:

MARC::Spec.find('650$a{$x}', marc_record)
# => [#<MARC::Subfield:0x00007ffa17999878 @code="a", @value="Arithmetic">, #<MARC::Subfield:0x00007ffa1798acb0 @code="a", @value="Arithmetic">] 

Note that this 650$a{$x} could also be written 650$a{?$x}; the ? ("exists") operator is implicit if no other operator is specified.

Find the first seven characters of 260$b, but only if the corresponding $a contains the string San Diego and there is at least one 050$b containing as a substring characters 7 through 10 of the 008 field:

MARC::Spec.find('260$b/0-7{$a~\San\sDiego}{050$b~008/7-10}', marc_record)
# => ["Harcourt"]

For further examples, see the MARCSpec documentation.