[ubuntu] How to search for text files only ?

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http://ubuntuforums.org – I've found out this is not as easy as I thought at first:on the other OS we know,all text files end with the .txt extension,which makes searching for them quite straightforward-no such thing on Linux,so how can I search for text files in a directory where they may be (and actually are) intermixed with all kinds of other files ? Typically (despite using Tomboy as well) I take lots of unorganized notes as short text files,which then end up somewhere in my home directory,then at some point I'd want to grep for a search term or string among all these files,but there's all sorts of other fi (Hardware)