Regular Expression

Four tips for learning regular expressions bit.ly/Xn7UH

Using regular expressions in PowerShell johndcook.com/blog/powershel…

If you're going to work with regular expressions, it's worthwhile to learn Perl notation even if you don't intend to ever use Perl.

You can include comments inside a regex with (?# ... ). For example, /the\s+(?# One or more spaces)end

[a-z] matches all lower case letters. [-az] matches '-', 'a', or 'z'.

Perl stores the content of the previous match in $&, the text to the left of the match in $`, and the text to the right in $'.

Grep rewritten in Perl (and so it supports Perl regular expressions) johndcook.com/blog/2021/03/0…

Regular expressions in Rust docs.rs/regex/latest/r…

The greatest regex trick ever rexegg.com/regex-best-tri…

If a dash is the first or last character in a character class, it is a literal dash and does not indicate a range.

Unusual applications of regular expressions cs.stackexchange.com/questions/1252…

'Perl Best Practices' recommends always using /xms on regexes. /x to allow whitespace & comments, /m and /s to handle newlines as expected.

Special characters and regular expressions johndcook.com/blog/2019/08/3…

Regex literals optimization nitely.github.io/2020/11/30/reg…

vi and vim's engine uses \+ and \= in place of the more common + and ?.

*, +, and ? are considered greedy quantifiers. They are going to consume matching tokens before moving on to the next atom.

"I define UNIX as '30 definitions of regular expressions living under one roof.'" — Donald Knuth

Parentheses have the side effect of capturing, setting \1 to the stuff matched by the first set of parentheses, \2 to the second, etc.

Regular expression to match medical diagnosis codes johndcook.com/blog/2019/05/0…

Parentheses and | denote options. Example: /(red|green|blue) truck/ matches 'red truck' or 'green truck' or 'blue truck'.

Reminder: * means zero or more, + means one or more, ? means zero or one.