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marc is a ruby library for reading and writing MAchine Readable Cataloging (MARC). More information about MARC can be found at


require 'marc'

# reading records from a batch file
reader ='marc.dat', :external_encoding => "MARC-8")
for record in reader
  # print out field 245 subfield a
  puts record['245']['a']

# creating a record 
record =
record.append('100', '0',  ' ', ['a', 'John Doe']))

# writing a record
writer ='marc.dat')

# writing a record as XML
writer ='marc.xml')

# encoding a record
MARC::Writer.encode(record) # or record.to_marc

MARC::Record provides #to_hash and #from_hash implementations that deal in ruby hash's that are compatible with the marc-in-json serialization format. You are responsible for serializing the hash to/from JSON yourself.


gem install marc

Or if you're using bundler, add to your Gemfile

gem 'marc'

Character Encodings in 'binary' ISO-2709 MARC

The Marc binary (ISO 2709) Reader (MARC::Reader) has some features for helping you deal with character encodings in ruby 1.9. It is always recommended to supply an explicit :external_encoding option to MARC::Reader; either any valid ruby encoding, or the string "MARC-8". MARC-8 input will by default be transcoded to a UTF-8 internal representation.

MARC::Reader does not currently have any facilities for guessing encoding from MARC21 leader byte 9, that is ignored.

Consult the MARC::Reader class docs for a more complete discussion and range of options.

The MARC binary Writer (MARC::Writer) does not have any encoding-related features -- it's up to you the developer to make sure you create MARC::Records with consistent and expected char encodings, although MARC::Writer will write out a legal ISO 2709 either way, it just might have corrupted encodings.


Source code at:

Find generated API docs at:

Run automated tests in source with rake test.

Developers, release new version of gem to rubygems with rake release (bundler-supplied task). Note that one nice thing this will do is automatically tag the version in git, very important for later figuring out what's going on.


Kevin Clarke Bill Dueber William Groppe Ross Singer Ed Summers