Regular Expression
@RegexTip
Learn to use regular expressions by following RegexTip. From @JohnDCook.
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\< represents a beginning word boundary and match a position between two tokens. Some engines don't support this.
\b matches a word boundary; \B matches anything but a word boundary.
Don't confuse \1 with $1. \1 is used inside a regex; $1 (in Perl) is used outside the regex after a match.
Many languages support Perl 5 regular expressions. For example, Microsoft .NET supports Perl 5 regex with some of its own extensions.
\d represents the numerical characters, or [0123456789]. Its complement is \D.
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…
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 ?.
![Il_Canone's profile picture. [S]’il y a une chose en mathématique qui (...) me fascine plus que toute autre, ce n’est ni “le nombre”, ni “la grandeur”, mais toujours la forme. Grothendieck](https://pbs.twimg.com/profile_images/1340681936340193282/QBXtXE2Z.jpg)
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