We must also take note that the project could have a capital “P”. Regular expressions are definitely a trade worth learning. For a good table of metacharacters, quantifiers and useful regular expressions, see this microsoft page. offers daily e-mail updates about R news and tutorials on topics such as: Data science, Big Data, R jobs, visualization (ggplot2, Boxplots, maps, animation), programming (RStudio, Sweave, La Te X, SQL, Eclipse, git, hadoop, Web Scraping) statistics (regression, PCA, time series, trading) and more...Remember, in R you have to double escape metacharacters!
Most regular expression implementations employ comparable syntaxes and metacharacters (generally influenced by the regex syntax of a programming language called Perl), and they behave similarly for most pattern-matching in this lesson.
But there are differences, often subtle, in each, so it’s always a good practice to read the application or language’s documentation whenever available, especially when you start using more advanced regex features.
A metacharacter is any American Standard Code for Information Interchange (ASCII) character that has a special meaning.
By using metacharacters and possibly literal characters, you can construct a regex for finding strings or files that match a pattern rather than a specific string.
How do those two files and the three files we want differ?
Well the files we want all start with “project-” or “project_” where as the other two don’t.
When you finish, split your team into two groups and write each other some tests.
These should include a) strings you want the other team to write regex for and b) regular expressions you want the other team to work out what they would match. If you want to check your logic use regex101, myregexp, regex pal or regexper.com: the first three help you see what text your regular expression will match, the latter visualises the workflow of a regular expression.
That notation is called “escaping” the special character.
The concept of “escaping” special characters is shared across a variety of computational settings, including markdown and Hypertext Markup Language (HTML).