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2.2 Other search engines<br />
Koders uses ctags, a widely used FLOSS tool for indexing source code, to build its<br />
search index 7 . Due to Koders’ use of ctags, only code which is written in one of the<br />
41 languages which ctags supports 8 is present in Koders’ index. <strong>Search</strong>es are always<br />
case-insensitive and regular expressions are not supported. However, one can search<br />
specifically for class names (e.g. cdef:parser), method names, interface names and<br />
combinations thereof.<br />
Koders uses a proprietary heuristic to rank code: “Essentially, the more reuse a code<br />
file receives, the more likely it will appear higher in your search results.” 7<br />
ohloh code http://code.ohloh.net is the successor to Koders. ohloh code indexes the<br />
projects which are registered at the open source directory site ohloh, currently also<br />
owned by Black Duck Software.<br />
The search features are very similar to those of Koders.<br />
Krugle http://krugle.org is the public code search engine of Krugle, a code search company<br />
which was acquired by Aragon Consulting Group in 2009. Krugle’s product is<br />
Krugle Enterprise, a searchable source code library 9 .<br />
Features of Krugle include searching for function calls, function definitions, class<br />
definitions, within certain projects, by document type, within a specific time period<br />
and by license.<br />
Krugle’s corpus consists of a mere 450 open source projects 10 .<br />
Google <strong>Code</strong> <strong>Search</strong> Starting out as the intern summer project of Russ Cox [2] , Google<br />
<strong>Code</strong> <strong>Search</strong> was the first public search engine to offer regular expression searches over<br />
public source code. It was launched in October 2006 and was shut down in January<br />
2012 “as part of Google’s efforts to refocus on higher-impact products” [2] .<br />
<strong>Search</strong> features include filtering by license, file path, package, class or function (or any<br />
combination) 11 . Every filter supports regular expressions 12 .<br />
A version of Google <strong>Code</strong> <strong>Search</strong> which operates on all repositories hosted at Google<br />
<strong>Code</strong> is still available at http://code.google.com/codesearch.<br />
The description of its inner workings and the availability of an open-source re-implementation<br />
of its tools were the main motivations for this work.<br />
8 http://ctags.sourceforge.net/languages.html<br />
9 http://venturebeat.com/2009/02/17/aragon-buys-software-code-analysis-co-krugle/<br />
10 http://www.krugle.org/projects/<br />
11 http://code.google.com/codesearch<br />
12 http://www.google.com/intl/en/help/faq_codesearch.html#regexp<br />
5
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