In an earlier review for FileSearchy commenter smaragdus wondered out loud if there are any utilities that support searching in epub (and fb2) files. Indeed the search for such a tool seems to confirm that it is a rare feature. I stumbled upon dnGREP, however.
dnGREP searches inside most text files and some like pdf require a plugin which come with the program and reside in the program’s folder. It integrates with the right click menu, can search plain text, Word documents, inside archives and more. It wasn’t clear at first if the latter includes epub files, then I found a support question or feature request that was answered:
You can enable this by modifying C:\Program Files\dnGREP\Plugins\dnGREP.Engines.Archive.plugin file.
Just add epub to the list of extensions.
The result can be seen in the screenshot above. dnGREP provides a a preview and highlights results, supports regular expressions and xpath. The user can also filter the search (icon to the far right of the Search in section) to restrict the search to specific path or type of files. Replace is supported and the >> button to the right of the Replace button provides custom actions such as Copy files, Move files, Delete files and File names to clipboard, Save as CSV and CSV to clipboard to copy the result file names for use elsewhere. The bookmark saves search queries for the future.
The program’s options includes such settings as Show file path in results, Show results tree expanded and Show result lines in context X before and X after.
Version 2.7.1 beta 2 used for this review, version 2.6.3 stable is also available for both 32 and 64 bit systems. Unfortunately, because it is usually better but difficult to avoid, dnGREP requires the .NET framework 4.0. dnGREP can be launched via the command line.