Objective 7: Search Text Files Using Regular Expressions

Linux offers many tools for system administrators to use for processing text. Many, such as sed, awk, and perl, are capable of automatically editing multiple files, providing you with a wide range of text-processing capability. To harness that capability, you need to be able to define and delineate specific text segments from within files, text streams, and string variables. Once the text you’re after is identified, you can use one of these tools or languages to do useful things to it.

These tools and others understand a loosely defined pattern language. The language and the patterns themselves are collectively called regular expressions (often abbreviated just regexp or regex). Regular expressions are similar in concept to file globs, but many more special characters exist for regular expressions, extending the utility and capability of tools that understand them.

Two tools that are important for the LPIC Level 1 exams and that make use of regular expressions are grep and sed. These tools are useful for text searches. There are many other tools that make use of regular expressions, including the awk, Perl, and Python languages and other utilities, but you don’t need to be concerned with them for the purpose of the LPIC Level 1 exams.

Regular expressions are the topic of entire books, such as Mastering Regular Expressions (O’Reilly). Exam 101 requires the use of simple regular expressions and related tools, specifically to perform ...

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