"...In this article let us review 15 practical examples of GNU grep command that will be very useful to both newbies and experts..." -- See also Introduction to the GNU/Linux Command Line:
* flossmanuals
* GNU Press

The grep search utility is one of the most essential building blocks of command line text filtering and processing. In this tutorial, we will give you a few simple examples.

Global Regular Expression Print is the rather un-catchy full name of grep, the staple of any Linux users toolkit. It is a search tool run from the command line that is evolved directly from Unix, and is so useful it deserved a post of its own.

You can direct grep to search through one file or many. You can also pipe in output from some other utility so that you’ll see only the information that you want to see. And, the fact that grep uses regular expressions allows you to perform searches even when you only have an approximate idea of what you’re searching for.

The grep command is a hugely powerful way to search through files. Like many command line utilities, once you're comfortable using it, you will discover that it is surprisingly fast and accurate.

Some interesting ways to use grep to shorten your command lines. Not to be confused with efficiency ;)

grep is a tool to search for strings inside a file. This release fixes an unexpectedly large number of flaws, from outright bugs (surprisingly many, considering this is "grep") to some occasionally debilitating performance problems. Special thanks to Paolo Bonzini for doing most of the heavy lifting.

This article covers two beneficial Linux tools, grep and sed. If searching for or handling text, grep and sed can increase your efficiency with Linux bash scripting and configuration files. We'll learn how to use these commands and get some helpful tips, too.

Here's a brief example of applying a regex, drawn from the UNIX command-line utility grep, which searches for a specified pattern among the content of one or more UNIX text files. The command grep -i -E '^Bat' searches for the sequence beginning-of-line (indicated with the caret, [^]), followed immediately by upper- or lowercase letters b, a, and t (the -i option ignores case in pattern matches, so B and b are equivalent, for instance). Hence, given the file heroes.txt: