By default grep do not supports regex patterns.
In this tutorial, we will examine how to use for regex patterns. grep provides a simple glob search but also provides regex support which is very useful for complex search ant matches. The Emacs command colors the output and makes found lines clickable: When you click a search hit, Emacs visits the target file at the occurrence. GNU grep supports the -P option to interpret PCRE patterns. Therefore, if we want the grep command to match PCRE, for instance, “ \d“, we should use the -P option: $ grep -P '\d' input.txt grep is a very popular tool used to match given search patterns in the given text. The Emacs ‘grep’ command lets you run the Unix or GNU/Linux ‘grep’ program, which searches files for lines that match a regular expression (regexp). Otherwise, grep will search the literal ‘|’ character. Note that we shouldn’t escape the ‘|’ when we pass the -E option to grep. Let’s do the same test with the -E option: $ grep -E 'awesome|powerful' input.txt
F, -fixed-strings list of fixed strings -G, -basic-regexp basic regular expression (default) -E, -extended-regexp extended regular expression -P, -perl-regexp perl compatible regular.
Grep allows us to use the -E option to interpret patterns as ERE. The one-page guide to GNU grep: usage, examples, links, snippets, and more. For example, we can match a line containing either “ awesome” or “ powerful“: $ grep 'awesome\|powerful' input.txtĪs we’ve seen in the command above, we’ve escaped the ‘|’ character to give it special meaning. That is to say, if we don’t set an option, it only supports BRE syntax. Grep is by default in GNU BRE matching mode.