DXR is described as 'code search and navigation tool aimed at making sense of large projects like Firefox. It supports full-text and regex searches as well as structural queries like "Find all the callers of this function' and is an app in the Online Services category. There are four alternatives to DXR for Linux, Self-Hosted solutions, Windows, Mac and Online / Web-based. The best alternative is Text Sherlock, which is both free and Open Source. Other great apps like DXR are Insight.io (Free Personal), OpenGrok (Free, Open Source) and LXR (Free, Open Source).
Provides a fast, easy to install and use search engine for text but, mostly for source code. OpenGrok requires to much time to install (though it may be worth it for some). Sherlock will give you a much easier setup, a text indexer, and a web app interface for searching.
Web-based code search and browsing platform which understands your code just like your IDE does and works out of the box. You can view the source code of hundreds of popular projects such as Apache Hadoop or Android.
LXR Cross Referencer, usually known as LXR, is a general-purpose source code indexer and cross-referencer that provides web-based browsing of source code, with links to the definition and usage of any identifier.