Hysterical Raisens Part of the answer may involve the origins of REs in practical computing. They were originally a theoretical concept from automata theory and formal language theory until Ken Thompson himself wrote a real implementation and used them in qed and ed(1). The original version had only the greedy syntax and so there wasn’t … Read more
First, even if the resulting regex will not keep the same meaning, let’s reduces regexes to \s*0 and \s+0 and use (” ” x 4) . “_0″ as an input. For the sceptics, you can see here that the lag is still present. Now let’s consider the following code: $x = (” ” x 4) … Read more
Update: from version 5.9 (build time Mar, 31. 2011), Notepad++ supports non greedy regular expressions (new scintilla 2.5).
Common credit card vendor regular expressions: Amex Card: ^3[47][0-9]{13}$ BCGlobal: ^(6541|6556)[0-9]{12}$ Carte Blanche Card: ^389[0-9]{11}$ Diners Club Card: ^3(?:0[0-5]|[68][0-9])[0-9]{11}$ Discover Card: ^65[4-9][0-9]{13}|64[4-9][0-9]{13}|6011[0-9]{12}|(622(?:12[6-9]|1[3-9][0-9]|[2-8][0-9][0-9]|9[01][0-9]|92[0-5])[0-9]{10})$ Insta Payment Card: ^63[7-9][0-9]{13}$ JCB Card: ^(?:2131|1800|35\d{3})\d{11}$ KoreanLocalCard: ^9[0-9]{15}$ Laser Card: ^(6304|6706|6709|6771)[0-9]{12,15}$ Maestro Card: ^(5018|5020|5038|6304|6759|6761|6763)[0-9]{8,15}$ Mastercard: ^(5[1-5][0-9]{14}|2(22[1-9][0-9]{12}|2[3-9][0-9]{13}|[3-6][0-9]{14}|7[0-1][0-9]{13}|720[0-9]{12}))$ Solo Card: ^(6334|6767)[0-9]{12}|(6334|6767)[0-9]{14}|(6334|6767)[0-9]{15}$ Switch Card: ^(4903|4905|4911|4936|6333|6759)[0-9]{12}|(4903|4905|4911|4936|6333|6759)[0-9]{14}|(4903|4905|4911|4936|6333|6759)[0-9]{15}|564182[0-9]{10}|564182[0-9]{12}|564182[0-9]{13}|633110[0-9]{10}|633110[0-9]{12}|633110[0-9]{13}$ Union Pay Card: ^(62[0-9]{14,17})$ Visa Card: ^4[0-9]{12}(?:[0-9]{3})?$ Visa Master Card: … Read more
This is an excellent question, and it took me a while to see the point of the lazy ?? quantifier myself. ? – Optional (greedy) quantifier The usefulness of ? is easy enough to understand. If you wanted to find both http and https, you could use a pattern like this: https? This pattern will … Read more
For a regular expression like .* or .+, append a question mark (.*? or .+?) to match as few characters as possible. To optionally match a section (?:blah)? but without matching unless absolutely necessary, use something like (?:blah){0,1}?. For a repeating match (either using {n,} or {n,m} syntax) append a question mark to try to … Read more
On greedy vs non-greedy Repetition in regex by default is greedy: they try to match as many reps as possible, and when this doesn’t work and they have to backtrack, they try to match one fewer rep at a time, until a match of the whole pattern is found. As a result, when a match … Read more
You’re looking for a non-greedy (or lazy) match. To get a non-greedy match in regular expressions you need to use the modifier ? after the quantifier. For example you can change .* to .*?. By default grep doesn’t support non-greedy modifiers, but you can use grep -P to use the Perl syntax.
You seek the all-powerful *? From the docs, Greedy versus Non-Greedy the non-greedy qualifiers *?, +?, ??, or {m,n}? […] match as little text as possible.
The non-greedy regex modifiers are like their greedy counter-parts but with a ? immediately following them: * – zero or more *? – zero or more (non-greedy) + – one or more +? – one or more (non-greedy) ? – zero or one ?? – zero or one (non-greedy)