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Chapter 9. Pattern Matching

A number of Linux text-editing utilities let you search for and, in some cases change, text patterns rather than fixed strings. These utilities include the editing programs ed, ex, vi, and sed; the awk scripting language; and the commands grep and egrep. Text patterns (also called regular expressions) contain normal characters mixed with special characters (also called metacharacters).

Perl's regular expression support is so rich that it does not fit into the tables in this chapter; you can find a description in the O'Reilly books Perl in a Nutshell, Perl 5 Pocket Reference, or Programming Perl. The Emacs editor also provides regular expressions similar to those shown in this chapter.

ed and ex are hardly ever used as standalone, interactive editors nowadays. But ed can be found as a batch processor invoked from shell scripts, and ex commands often are invoked within vi through the colon (:) command. We use vi in this chapter to refer to the regular expression features supported by both vi and the ex editor on which it is based.

sed and awk are widely used in shell scripts and elsewhere as filters to alter text.

This chapter presents the following information:

  • Filenames versus patterns

  • List of metacharacters available to each program

  • Description of metacharacters

  • Examples

A thorough guide to pattern matching can be found in the Nutshell handbook Mastering Regular Expressions by Jeffrey E. F. Friedl.



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