Goin Full Text Search for your files
Goin is a full text search indexer using https://github.com/blevesearch/bleve for your files on disk. It can handle plain text, many different images, as well as pdf files if the correct utilities are installed.
It processes files based on their mime type making it fairly easy to add support for more files in the future. It's still very much a work in progress.
goin --index file.txt /path/to/directory/ another.file /another/directory
goin --query +word -word \"phrase made up of multiple words\" field:word
Full details of the query syntax can be found at: https://github.com/blevesearch/bleve/wiki/Query%20String%20Query
goin --help will give you an overview of the flags to tweak it's operation.
Depending on how you install them you may have to set the CGO_CFLAGS and CGO_LDFLAGS environment variables to tell cgo where to find them.
go doc cmd/go will give you more information on configuring cgo for your environment.
For pdf support goin needs a few extra items. The (ImageMagick):"http://www.imagemagick.org/" convert tool as well as the (xpdf):http://www.foolabs.com/xpdf/" suite of tools. Goin uses these first to try to get text out of the pdf and falling back to OCR if the pdf is only images.
go get bitbucket.org/zaphar/goin will install the tool.