When a terminal gives you too much

Linux command-line tools are generous: they hand you the whole file, the whole log, the whole configuration. Most of the time you only care about the few lines that match a keyword. That is the job of grep — described in the source as probably the most widely used text manipulation command in Linux.

grep lets you filter the content of a file for display. Give it a keyword and a source of text, and it returns only the lines that contain that keyword. Everything else is hidden.