Regex

Regular expressions specify a match patter in a text.

They can be used for example with grep, rg, find, fd, vim, etc.

Similar expressions are also used for Git (.gitignore) and containerization (.containerignore) which we will learn about later.

Here are some of the most important building blocks:

• ^: Start of line
• $: End of line
• (): Group
• |: Alternation
• [abcd]: Character set, here a until d
• [a-z]: Character range, here a until z
• [^b-h]: Negated character range, here b to h
• .: Any character
• .*: 0 or more characters
• .+: 1 or more characters
• \w: Letter or number
• \W: Neither letter nor number
• \d: Digit
• \D: Not digit
• \s: Whitespace
• \S: Not whitespace

Writing regular expressions is not easy, but there are many (online) tools that you can use to test and debug your regex.