ack!

Agent Ransack is a tool for finding files and information on your hard drive fast and efficiently. When searching the contents of files Agent Ransack also displays the text found. Users can then quickly browse the results without having to separately open each file!

dnGrep allows you to search across files with easy-to-read results. Search through text files, Word documents, PDFs, and archives using text, regular expression, XPath, and phonetic queries. dnGrep includes search-and-replace, whole-file preview, right-click search in File Explorer, and much more.

ripgrep is a command line search tool that combines the usability of The Silver Searcher (an ack clone) with the raw speed of GNU grep.

Silver Searcher is a code search tool similar to ack that claims to be much faster. It's implemented in C and has some extra features such as ignoring files per .hignore, .gitignore contents.

Baloo is not an application, but a daemon to index files. Applications can use the Baloo framework to provide file search results.

mawk is an interpreter for the AWK Programming Language.

UniversalCodeGrep (ucg) is an extremely fast grep-like tool specialized for searching large bodies of source code. It is intended to be largely command-line compatible with Ack, to some extent with ag, and where appropriate with grep. Search patterns are specified as PCRE regexes.