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Catmandu::Introduction - An Introduction to Catmandu data processing toolkit

Catmandu::Introduction(3pm) User Contributed Perl Documentation Catmandu::Introduction(3pm)


Catmandu::Introduction - An Introduction to Catmandu data processing toolkit


Catmandu is a data processing toolkit developed as part of the LibreCat <> project. Catmandu provides the command line client catmandu and a suite of tools to ease the import, storage, retrieval, export and transformation of data. For instance, to transform a CSV file into JSON use the command:
    $ catmandu convert JSON to CSV < data.json
Or, to store a YAML file into an ElasticSearch database type (requires Catmandu::ElasticSearch):
    $ catmandu import YAML to ElasticSearch --index_name demo < test.yml
To export all the data from an Solr search engine into JSON type (requires Catmandu::Solr):
    $ catmandu export Solr --url http://localhost:8983/solr to JSON
With Catmandu one can import OAI-PMH records in your application (requires Catmandu::OAI):
    $ catmandu convert OAI --url --set allFtxt
and export records into formats such as JSON, YAML, CSV, XLS, RDF and many more.
Catmandu also provides a small scripting language to manipulate data, extract parts of your dataset and transform records. For instance, rename fields with the 'move_field' Fix command:
    $ catmandu convert JSON --fix 'move_field(title,my_title)' < data.json
In the example above, we renamed all the 'title' fields in the dataset into the 'my_title' field.
One can also work on deeply nested data. E.g. create a deeply nested data structure with the 'move_field' Fix command:
    $ catmandu convert JSON --fix 'move_field(title,my.deeply.nested.title)' < data.json
In this example we moved the field 'title' into the field 'my', which contains a (sub)field 'deeply', which contains a (sub)field 'nested'.
Catmandu was originally created by librarians for librarians. We process a lot of metadata especially library metadata in formats such as MARC, MAB2 and MODS. With the following command we can extract data from a marc record and to store it into the title field (requires Catmandu::MARC):
    $ catmandu convert MARC --fix 'marc_map(245,title)' < data.mrc
Or, in case only the 245a subfield is needed write:
    $ catmandu convert MARC --fix 'marc_map(245a,title)' < data.mrc
When processing data a lot of Fix commands could be required. It wouldn't be very practical to type them all on the command line. By creating a Fix script which contains all the fix commands complicated data transformations can be created. For instance, if the file "myfixes.txt" contains:
then they can be executed on a MARC file using this command:
    $ catmandu convert MARC --fix myfixes.txt < data.mrc
Fixes can also be turned into executable scripts by adding a bash 'shebang' line at the top. E.g. to harvest records from an OAI repository write this fix file:
     #!/usr/bin/env catmandu run
     do importer(OAI,url:"")
Run this (on Linux) by setting the executable bit:
     $ chmod 755 myfix.fix
     $ ./myfix.fix
To experiment with the Fix language you can also run the catmandu Fix interpreter in an interactive mode:
     $ catmandu run
     Catmandu 0.95 interactive mode
     Type: \h for the command history
     fix > add_field(hello,world)
     hello: world
     fix >
Catmandu contains many powerful fixes. Visit <> to get an overview what is possible.


For more information read our documentation pages <> and blog <> for a complete introduction and update into all Catmandu features.
In the winter of 2014 an Advent calendar tutorial was created to provide a day by day introduction into the UNIX command line and Catmandu:
If you need extra training, our developers regulary host workshops at library conferences and events: <>


There are several ways to get a working version of Catmandu on your computer. For a quick and demo installation visit our blog <> where a VirtualBox image is available containing all the Catmandu modules, including ElasticSearch and MongoDB.
On our website <> we provide installation instructions for:
Ubuntu Server
and even a generic installation using Docker <>: <>.

Open Source

Catmandu software published at is free software without warranty, liabilities or support; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 or any later version. Every contributor is free to state her/his copyright.

Developers & Support

Catmandu has a very active international developer community. We welcome all feedback, bug reports and feature enhancement.
Join our mailing list to receive more information: ""
Are a developer and want to contribute to the project? Feel free to submit pull requests or create new Catmandu packages!


Catmandu is created in a cooperation with many developers world wide. Without them this project isn't possible. We would like to thank our core maintainer: Nicolas Steenlant and all contributors: Christian Pietsch , Dave Sherohman , Friedrich Summann , Jakob Voss , Johann Rolschewski , Jorgen Eriksson , Magnus Enger , Maria Hedberg , Mathias Loesch , Najko Jahn , Nicolas Franck , Patrick Hochstenbach , Petra Kohorst , Snorri Briem , Upasana Shukla and Vitali Peil


2017-10-01 perl v5.26.0