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:

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.

Ack is designed as a replacement for 99% of the uses of grep. ack is intelligent about the files it searches. It knows about certain file types, based on both the extension on the file and, in some cases, the contents of the file.

There is a classic bit of computer wisdom that states “If you’ve got a problem, and decide to solve it with regular expressions, now you’ve got two problems.” This of course stems from the perception that regular expressions are a complicated mix of magic characters and Voodoo.

An invaluable guide to grep, a command line text search utility for GNU systems...

How do I use the Grep command with regular expressions under Linux operating systems?

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.

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.