Learn to use regular expressions by following RegexTip. From @JohnDCook.
Joined November 2009
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Jun 12
(?i) makes a regular expression case-insensitive. Example: (?i)abc is the same as [aA][bB][cC].
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Jun 11
In CSS, ^= means begins with, *= means contains anywhere, and $= means ends with.
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Jun 10
CSS has a crude form of regex, selection operators ^=, *=, and $= analogous to the use of ^, *, and $ in regex.
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The acronym PCRE stands for 'Perl Compatible Regular Expressions'.
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*?, ?, and ?? are lazy quantifiers. The regexp engine will attempt to match as few tokens as possible.
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In Perl, \A matches the beginning of a string and \z matches the end of a string. Removes ambiguity of lines vs strings.
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Emacs regex escape |, (, and ). For example, (a|b) in Perl becomes \(a\|b\) in Emacs.
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Flatten JSON files so they're easier to grep: github.com/TomNomNom/gron
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May 29
“Regular expressions aren’t random jumbles of punctuation—they’re carefully thought-out jumbles of punctuation!” -- The Perl Cookbook
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May 28
\> represents an ending word boundary and match a position between two tokens. Some engines don't support this.
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May 27
\< represents a beginning word boundary and match a position between two tokens. Some engines don't support this.
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May 25
\b matches a word boundary; \B matches anything but a word boundary.
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May 22
Don't confuse \1 with $1. \1 is used inside a regex; $1 (in Perl) is used outside the regex after a match.
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May 21
Many languages support Perl 5 regular expressions. For example, Microsoft .NET supports Perl 5 regex with some of its own extensions.
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May 20
\d represents the numerical characters, or [0123456789]. Its complement is \D.
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