The HTML content used for the demonstration follows. In this section, you'll see a variety of regular expressions executed against a single file of HTML. Running regular expressions using grep against a single HTML file
(dot) represents "any character" and the metacharacters \d represent any digit. You can think of a metacharacter as a placeholder symbol. When you declare a regular character in a regular expression, the regular expression engine searches content for the declared character.Ī metacharacter represents a group of characters or other aspects of searching. Examples include the letters a, g, or t, or the numerical digits 3 or 8. Regular characters versus metacharactersĪ regular character represents itself in the text you're searching.
#Regular expression grep how to
The last shows you how to use a special command-line utility named pcre2grep to execute regular expressions against text split over multiple lines in one or many HTML files. The second shows you how to work with multiple HTML files. The first shows you how to create regular expressions that execute against a single HTML file.
This article is divided into three sections. All you need to do is copy and paste an example onto the command line of a Linux terminal and you'll see results immediately.
#Regular expression grep code
The article uses grep because that won't require you to set up a particular coding environment or write any complex programming code to work with the examples of regular expressions demonstrated in this article. Thus, being able to apply regular expressions to HTML files is a useful skill. Matching and retrieving text from HTML is a common task for a broad variety of IT professionals, particularly when troubleshooting issues in web pages. This article uses the features described in the previous articles, along with new ones, to match and filter content in HTML files. The second discussed working with quantifiers, pattern collections, groups, and word boundaries in regular expressions. The first article in this series described the basics of using metacharacters and regular characters to create regular expressions. The grep command filters content in a file or as output from stdout. This article is a third in a series about executing regular expressions using the grep executable that ships with Linux operating systems.
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