Code Search Engines: How They Work and 5 Tools You Should Know

What Is a Code Search Engine?

A code search engine is a specialized tool that helps software developers find specific sections of program code. It functions much like a traditional search engine, but is tailored specifically for finding code. 

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Given the vast amount of open-source code available on the internet, and large codebases maintained by many companies, code search engines provide a valuable resource for developers. They can help developers find code snippets, libraries, and frameworks that can help them solve a problem in their projects, or discover specific areas of code they need to reference or work on.

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Code search engines provide functionality that goes beyond basic text search. They provide context-aware search capabilities, understanding the semantics of different programming languages, and often providing features like code indexing, code syntax highlighting, and even the ability to visually navigate through complex codebases.

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This is part of a series of articles about code visualization.

Core Components of Code Search Engines

Crawlers

Crawlers, also known as spiders or bots, are the first step in the code search process. These are automated programs that visit web pages and repositories to locate and fetch code. They navigate through the web, following links and collecting data.

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Crawling enables the collection of a vast amount of code from various sources. Code-specific crawlers are designed to understand the structure of different file types and programming languages, enabling them to extract relevant code snippets and metadata from the files they encounter.

Indexer

Once the crawlers have fetched the code, the next step is indexing. The indexer is responsible for organizing the collected data in a way that facilitates fast and accurate searches. It creates an 'index', a data structure that maps each unique word or token found in the code to the locations where it appears.

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The indexer also applies various transformations to the data to make it easier to search. This may include converting all text to lower case, removing common 'stop words', and applying other normalization techniques. The end product is an optimized index that allows for fast retrieval of huge volumes of code.

Query Processor

The query processor is the component that handles user search requests. When a user enters a search query, the query processor interprets the query, accesses the index created by the indexer, and retrieves the relevant results. The processor applies algorithms to determine the relevance of each piece of code to the query, often taking into account factors such as the frequency of the search terms in the code, the location of the terms, and so on.

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The query processor also handles the presentation of the search results, ranking them based on their relevance and often providing additional information such as a brief excerpt of the code, the programming language used, and a link to the source.

User Interface

Last but not least, the user interface (UI) is the component of the code search engine that users interact with. It provides a platform for users to enter their search queries and view the results. The UI is designed to be intuitive and user-friendly, making it easy for developers to find the code they are looking for.

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The UI typically includes features such as autocomplete, syntax highlighting, and the ability to filter results by language, license, or other criteria. Some interfaces also provide advanced features like the ability to navigate through the code base of a project, allowing developers to explore related portions of code and understand their context.

Notable Code Search Engines

1. Github

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As one of the world's largest repositories of open-source software, Github is a natural place to start when searching for code. Its built-in search functionality allows developers to search through millions of repositories, making it a gold mine of code snippets, libraries, and frameworks.

Github's code search engine lets you filter by language, repository, user, and more, but lacks some of the advanced features of dedicated code search solutions, as we’ll show below. However, a key advantage of GitHub as a code search engine is that it’s also a social platform, where developers can vote on projects (by adding stars), share their work, and learn from each other. This makes it possible to find code that is not only relevant to a search, but is also valued by fellow developers.

2. CodeSee

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CodeSee aims to make understanding and navigating through codebases easier by providing a visual overview of the code. This can be particularly helpful for developers who are new to a project and need to get up to speed quickly.

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CodeSee includes a code search engine that lets you search for specific functions, variables, or even comments within the code. The search results are presented in a visually intuitive manner, with the relevant parts of the code highlighted for easy identification.

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What sets CodeSee apart from other code search engines is its map feature. The CodeSee Map provides a visual representation of your codebase, showing how different parts of the code are interconnected. This can be helpful for understanding the overall architecture of the project and identifying problems or areas of improvement.

3. Codase

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Codase is a code search engine that aims to make searching for source code as easy as searching for anything else on the web. Unlike Github, Codase isn't tied to a particular repository or platform, and instead indexes code from a variety of sources, including open source projects and proprietary code.

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Codase understands the structure and semantics of code, which allows it to provide more accurate and relevant results than a simple keyword search. You can search for specific functions, classes, methods, or other constructs within code. Codase also lets you search for code by its usage and filter results by programming language.

4. Sourcegraph

Sourcegraph is another code search engine that allows developers to search for code across multiple repositories. It's specifically designed for teams and organizations with large codebases, but it's also useful for individual developers.

Sourcegraph provides universal code search, which means it can search for code across different repositories, languages, and platforms. This feature can be helpful when you're working on a complex project with multiple components written in different languages or frameworks.

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Additionally, Sourcegraph integrates with popular code hosting platforms like Github, Gitlab, and Bitbucket. This integration allows you to search for your proprietary code across repositories hosted by these platforms.

5. Krugle

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Krugle is a code search engine that caters to the needs of developers and teams working on complex software projects. Its main purpose is to facilitate the discovery and reuse of open source and internal source code. 

Krugle works by indexing both publicly available code repositories and private codebases, providing a centralized platform for code search. This approach allows developers to access resources ranging from open-source projects to their organization’s proprietary code.

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One of the key features of Krugle is its ability to index not just the code itself, but also the accompanying technical documentation and comments within the code. This allows developers to search not only code snippets that match their query, but also the explanations and context surrounding those snippets. Krugle also lets developers search for code by license types, which can be useful to find code that meets enterprise standards.