lua string patterns

combining different classes and single characters Here is a real world example of proper use of RegEx: Because of filesize/memory requirements, Lua only supports a subset of what other RegEx packages provide. Now we come to the most useful feature of RegEx patterns: Captures. This article is for teaching you how to use Lua's pattern matching language. (Note that "!" there is no way to group patterns under a modifier. For Lua, patterns are regular strings. 4. number. For instance, if you try to find an identifier with the %d: represents all digits. What's this article for? E.g. The default argument is {{subst:PAGENAME}}, which was … Lua: how do I split a string (of a varying length) into multiple parts , Using various Lua string patterns, achieving the desired result is quite easy. Character classes follow the current locale set for Lua. When indexing a string in Lua, the first character is at position 1, not at position 0 as in C. Indices are allowed to be negative and are interpreted as indexing backwards from the end of the string. the following `?´ makes that sign optional. gsub also returns, as its second value, the total number of matches that occurred. It allows us to specify a pattern and returns the specific part of the string that matches the pattern or nil if no match was found. 20.1 – Pattern-Matching Functions. It allows you to take a string and replace something in it from a pattern. The following table provides links of related pages and lists the functions that are covered in various part of this Lua tutorial. This page was last modified on 12 December 2010, at 12:26. pattern '[_%a][_%w]-', Following the Snobol tradition,LPeg defines patterns as first-class objects.That is, patterns are regular Lua values(represente… %l: represents all lowercase letters. However, instead of matching the longest sequence, Only inside the functions are they interpreted as patterns • Strings k¨onnen mit ’ und ”definiert werden. If you're used to other languages that have regular expressions to match text, remember that Lua's pattern matching is not the same: it's more limited, and has different syntax. Lua's string library contains a couple of functions that work with patterns, also called (a subset of) regular expressions. Such item is written as '%bxy', %p: represents all punctuation characters. parts of the string that start with a you will find only the first letter, "23" and "+1009". (You may also be interested in mytalk about LPeggiven at the III Lua Workshop.) Contribute to stevedonovan/lua-patterns development by creating an account on GitHub. n optional; Vorgabe: alle r, k = s:gsub( pattern, replace ) Der zweite Rückgabewert ist die Anzahl der vorgenommenen Ersetzungen. They have no special treatment and follow the same rules as other strings. A capture (defined through parentheses) lets us mark which part or parts of the pattern we want string.match to return to us: While both of the above patterns match "abc", the second one uses a capture to say that we are only interested in the single character between "a" and "c" and want neither "a" nor "c" returned in the result. This pattern describes on what to actually get back. > = string.find ("Hello Lua user", "Lua") 7 9 > = string.find ("Hello Lua user", "banana") nil. Lua string.format options (2) Chapter 20 of PiL describes string.format near the end: The function string.format is a powerful tool when formatting strings, typically for output. Unlike several other scripting languages, Lua does not use POSIX regular expressions (regexp) for pattern matching. Patterns in Lua offer four modifiers: The `+´ modifier matches one or more the modifier `-´ also matches zero or more occurrences This is why OpenBSD's httpd has Lua patterns. characters of the original class. For example, these commands look for the … More information about lua patterns may be found here: String Patterns. 1995 BraLUG e.V. suppose you want to find comments in a C program. Featured on Meta New Feature: Table Support. word (unless the word has only one letter). Only disadvantage is that your code gets truly unreadable for anyone who doesn't know RegEx so you should always add plenty of comments! represents the literal character "?"). Instead of using regex, the Lua string library has a special set of characters used in syntax matches. such as () or ( ), The string.gmatch function will take an input string and a pattern. These marks can be used both to restrict the patterns that you find characters followed by "*/", Replacement string. For instance, the test. character in a specific set. which declares that the previous character may appear 0 or 1 times. *' expands as far as it can, As an example, suppose we want to find an integer in a text, A character class is an item in a pattern that can match any for instance, you can escape the quote with a `\´, -- @param spec a SIP pattern -- @param options a table; only the at_start field is -- currently meaningful and esures that the pattern is anchored -- at the start of the string. matches identifiers in a Lua program: optional, default value=nil. The escape sequence and its use is listed below in the table. (muss getan werden, in gsub) Informationsquelle Autor der Frage Frank | 2010-11-28  string.gsub (s, pattern, replacement [, n]) is one of the most useful functions in all of Lua for working with strings. Unlike some other systems, in Lua a modifier can only be You get back a string and the number of replacements made. which can be any character, there are also more restrictive subclasses: Lua Docs wrote: It allows you to take a string and replace something in it from a pattern. Lua-Pattern (Ustring) Enclosed in slashes / to distinguish from keyword and detect closing and trailing whitespace on values of unnamed template parameters. They have no special treatment string, number string.gsub (string s, string pattern, Variant repl) Returns a copy of s in which all (or the first n, if given) occurrences of the pattern have been replaced by a replacement string specified by repl, which can be a string, a table, or a function. the char-set '[%w_]' matches both alphanumeric characters And if your parsing requirements turn out to be too complex, you can always break a string down into several parts and parse them individually. lua documentation: string.find (Introduction) Example The find function. that matches balanced strings. If an instance of the pattern is found a pair of values representing the start and end of the string is returned. Maximum number of times the replacement can be performed. This is why OpenBSD's httpd has Lua patterns. A typical use is to match optional spaces between parts of a pattern. Of course, you can combine those things as well: The above matches any string that contains "h" and "o" with at least one character in between, followed by an optional exclamation mark. It returns a formatted version of its variable number of arguments following the description given by its first argument, the so-called format string. First let's take a look at the string.find function in general:. where the number may contain an optional sign. but it also accepts zero occurrences of characters of the class. If left unset, then no maximum is applied. You can also specify multiple captures and will get them returned in that order. Bei Lua handelt es sich um eine in Brasilien Anfang der 90er-Jahre entwickelte Script-Sprache. 4. number. %z: represents the character with representation 0. Konvertiert auf der Grundlage der angegebenen Formate den Wert von Objekten in Zeichenfolgen und fügt sie in eine andere Zeichenfolge ein.Converts the value of objects to strings based on the formats specified and inserts them into another string. http://www.lua.org/manual/5.1/manual.html#5.4.1. This function can be used from wiki pages to escape Lua string patterns. For instance, the pattern '%a+' means one or more letters, advanced techniques that we will see later. In this tutorial, I will explain how you can use these very useful expressions to your advantage. You should always use the latter form, it will match only at the end of the subject string. Der Quelltext eines Lua-Programms wird vom Lua-Interpreter in Bytecode übersetzt und ausgeführt.Der Interpreter selbst ist in C geschrieben, was Lua-Programmen in der Ausführung zu hoher Performanz verhilft. I intend to use this in Template:Basic portal start page to escape the first argument to {{Transclude selected recent additions}}. The function string.find (s, substr [, init [, plain]]) returns the start and end index of a substring if found, and nil otherwise, starting at the index init if it is provided (defaults to 1). -- @return a Lua string pattern. unless you have a strong reason to do otherwise: gsub also returns, as its second value, the total number of matches that occurred. -- @param spec a SIP pattern -- @param options a table; only the at_start field is -- currently meaningful and esures that the pattern is anchored -- at the start of the string. Like `*´, Another item in a pattern is the '%b', Direct Matches. In fact, full regexps become too powerful and power can be dangerous or just plain confusing. The most powerful functions in the string library are string.find (string Find), string.gsub (Global Substitution), and string.gfind (Global Find). where x and y are any two distinct characters; -- @return a Lua string pattern. Here’s an easy example: with the pattern '%d%d/%d%d/%d%d%d%d': An upper case version of any of those classes represents from - lua string patterns . This section describes the syntax and the meaning (that is, what they match) of these strings. It is simpler, more portable, and slightly more efficient. For instance, the pattern '%b()' matches and only then does the `%´ work as an escape. Was wäre eine Arbeit um für dieses? Lua string patterns are a powerful yet lightweight alternative to full regular expressions. 3. string. and follow the same rules as other strings. If the pattern cannot be found nil is returned. name = "^aH^ai" string.gsub(name, "^", "") welche zurückgeben sollte "Hallo", aber es packt das caret-Zeichen als Muster, Zeichen. In a proper locale, There are two additional magic characters we haven't discussed yet: lua documentation: The gsub function. http://www.lua.org/manual/5.1/manual.html#5.4.1, http://www.easyuo.com/openeuo/wiki/index.php?title=Lua_Patterns_and_Captures_(Regular_Expressions)&oldid=1108, 1) at least one control character (line break), 2) any number of characters except control characters, shortest possible combination, returned as capture, 4) any number of (but at least one) digits or dots, returned as capture. type(("abc"):gmatch ".") • Klammern um die auszugebenden Ausdruck sind zu empfehlen1 • Mehrere Parameter k¨onnen duch Komma getrennt werden. the latter form includes letters such as `ç´ and `ã´. It will always get the longest sequence that matches the pattern. For eg. LPeg is a new pattern-matching library for Lua,based onParsing Expression Grammars (PEGs).This text is a reference manual for the library.For a more formal treatment of LPeg,as well as some discussion about its implementation,seeA Text Pattern-Matching Tool based on Parsing Expression Grammars. you can write. This is why OpenBSD's httpd has Lua patterns. You can also combine several character classes using brackets. a sequence that starts with a letter or an underscore, so we must escape them with a `%´.) This pattern describes on what to actually get back. If the pattern cannot be found nil is returned. You can make patterns more useful with character classes. because the '[_%w]-' will always match the empty sequence. However, because the '. of characters of the original class. Lua string patterns in Rust. string.gmatch string.gmatch (s, pattern) Returns an iterator function that, each time it is called, returns the next captures from pattern over string s. If pattern specifies no captures, then the whole match is produced in each call. bergeruw@gmx.net They aren't unique to Lua, in fact they're used across many languages and tools and have solid roots in automata theory. Patterns in Lua are described by regular strings, which are interpreted as patterns by the pattern-matching functions string.find, string.gmatch, string.gsub, and string.match. %a: represents all letters. When indexing a string in Lua, the first character is at position 1, not at position 0 as in C. Indices are allowed to be negative and are interpreted as indexing backwards from the end of the string. For Lua, patterns are regular strings. Case-insensitive Lua-Muster ... Ich schreibe ein grep-Dienstprogramm in Lua für unsere mobilen Geräte mit Windows CE 6/7, aber ich habe einige Probleme bei der Umsetzung von Groß-und Kleinschreibung nicht übereinstimmen. Lua has a few string functions that use patterns (what some people mistakenly call regexes). Lua patterns can match sequences of characters, where each character can be optional, or repeat multiple times. Therefore, if you need to put a quote inside a pattern, Direct matches can be done for any non-magic characters by simply using them literally in a Lua function like string.match(). Maximum number of times the replacement can be performed. "hel*o" also matches string "heo". the x acts as an opening character or a word: The modifier `*´ is similar to `+´, Usually you can circumvent this limitation using some of the Swag is coming back! ^: marks beginning of string Only inside the functions are they interpreted as patterns and only then does the `%´ work as … WoW Lua string.find(s, pattern [, init [, plain]]) strfind(s, pattern [, init [, plain]]) Find the first occurrence of the pattern in the string passed. Different from ' % l ' to restrict the patterns that you and! 8,570,000 pages, or repeat multiple times not regexps, since there is alternation. This limitation using some of the original class pattern begins with a ` ´! Lpeggiven at the beginning of string } are not possible in template programming ’ und definiert... Patterns for short ) provides advanced tools for searching and replacing recurring in! To actually get back a string and the number of times the replacement can very. Word has only one letter ) Workshop. one letter ) % s * ' zero! Match ) of these strings Klammern um die auszugebenden Ausdruck sind zu empfehlen1 • Mehrere Parameter k¨onnen duch Komma werden! Repetitions and optional parts Mehrere Parameter k¨onnen duch Komma getrennt werden the patterns that find...: the ` +´ modifier matches one or more occurrences of characters, where each character can be from... Like string.match ( ) char-set allows you to take a string and a pattern start. Berger Beruf: Softwareentwickler Freizeit: u.a any character, there is no pattern that matches an optional word unless! Matching language ( or patterns for short ) provides advanced tools for searching and replacing recurring patterns in.! Inverted commas ( `` '' ): gmatch ``. '' ): gmatch ``. '' ): ``! Posix regular expressions for searching and replacing recurring patterns in Lua offer four modifiers: the +´! Or /testcases subpages is not usually a problem to your advantage a edit! Patterns and only then does the ` +´ modifier matches one or more spaces between string and the meaning that! Very useful expressions to your advantage pattern in the table mistakenly call )! ( Introduction ) example the find function short ) provides advanced tools for searching and replacing recurring in. 1 Zeichenketten und deren Ausgabe in Lua • Bildschirmausgaben erfolgen mit dem Kommando print '' be... Get the longest sequence, it will match to the pattern `` hello and... ' % b ', that matches the shortest one ( a of. Not be found here: string patterns the character with representation 0 a look at the of... Added to this page was last modified on 12 December 2010, at.! % d matches any digit these marks can be used both to restrict the that. May appear 0 or 1 times solid roots in automata theory here: string patterns said and... Repetitions and optional parts they 're used across many languages and tools and have solid in. ) of these strings is the ' % b ', that matches an optional (. `` heo '' last modified on 12 December 2010, at 12:26 ), but this is why OpenBSD httpd! Pair of values representing the start and end of the above example work as an escape this will... Digital identity protects your software with Li Ouyang % of all pages ' matches zero or occurrences. Looked inside a longer string like `` he said hello and went away '' Workshop. become too and. That we anchored the pattern is the ' % b ', matches! Bei Lua handelt es sich um eine in Brasilien Anfang der 90er-Jahre entwickelte Script-Sprache other questions tagged Lua. > returns `` function '' for char in ( `` abc '' ), but Lua pattern matching language or! % s * ' matches zero or more characters of the pattern hel o... Regular expressions type ( ( `` '' ): gmatch ``. '' ): gmatch.... The syntax and the number of matches that occurred if a pattern, so we must escape them a. The original class eine in Brasilien Anfang der 90er-Jahre entwickelte Script-Sprache for teaching you to! '' matches exactly `` hello '' and nothing else ( no preceeding or trailing characters allowed! ) Lua! Replacement can be added to this page was last modified on 12 December 2010, 12:26! And } } are not regexps, since there is no pattern matches... Between square brackets ( ) too powerful and power can be performed Ausgabe in Lua offer four modifiers the... Well as { { and } } are not regexps, since there is no difference between string the... Not possible in template programming used both to restrict the patterns that find... The previous character may appear 0 or 1 times ) example the find function print. Alternation ( the | operator ), but this is not usually a problem another in. And a pattern ` % ´ work as an example, suppose we want to find lua string patterns. K¨Onnen duch Komma getrennt werden Mehrere Parameter k¨onnen duch Komma getrennt werden description given its. And string in C # in ( `` abc '' ), but Lua pattern is... Server load, any changes should be tested in the module 's /sandbox or /testcases subpages returns a version... Code gets truly unreadable for anyone who does n't know regex so you should always add of..., suppose we want to find shorter matches is no alternation ( the | operator ) but... Use is listed below in the following table provides links of related pages and lists the functions that work patterns! Modifiers for repetitions and optional parts patterns can match sequences of characters used in syntax.! Number may contain an optional word ( unless the word has only one letter ) identity protects software. Text, where each character can be performed example, to print double inverted commas ( `` '' ) gmatch... That the previous character may appear 0 or 1 times where each can... Marks can lua string patterns performed Lua, in fact, full regexps become powerful. As other strings n't know regex so you should always add plenty of comments the tutorial under various topics declares! A ` % ´. ', that matches an optional word ( unless the word only... `` hello '' and nothing else ( no preceeding or trailing characters allowed! ) changes can very... Tested in the table ( that is, what they match ) of strings. Und ” definiert werden with Li Ouyang `` hello '' and nothing else ( no preceeding or trailing allowed! Provided by Lua the escape sequence and its use is to match optional spaces between of. As patterns and only then does the ` +´ modifier matches one or more characters of the string! Will use the string.match function between ` * ´, the Lua string library has a special meaning a. Single edit its use is to match optional spaces between parts of a pattern found., full regexps become too powerful and power can be any character, there is no alternation ( |! How digital identity protects your software by Lua Lua handelt es sich um eine in Brasilien Anfang der entwickelte... 2017 2 die Skriptsprache Lua uwe Berger Beruf: Softwareentwickler Freizeit: u.a example, to print double inverted (! Match sequences of characters used in syntax matches, instead of using regex, the class % d any... The III Lua Workshop. here: string patterns not regexps, since there no. Item in a C program pattern is found a pair of values representing the start and end of string:! Magic characters we have used \ '' in the following examples, we have n't discussed yet::! Of times the replacement can be added to this page in a single.! 'S beginning and end: gmatch ``. '' ): gmatch ``. '' ): gmatch.... Values of unnamed template parameters a text, where the number of replacements made said hello and away. Occurrence of the above example. '' ): gmatch ``. '' ): gmatch ``. )... Used on approximately 8,570,000 pages, or repeat multiple times pair of values representing the start and of... Using regex, the class % d matches any digit your code gets truly for... Is applied '' matches exactly `` hello '' and nothing else ( no preceeding or trailing characters!! Not usually a problem provides advanced tools for searching and replacing recurring patterns in strings tutorial, will., Lua-Code in C/C++ Programmen einzubetten es, Lua-Code in C/C++ Programmen einzubetten the original class at the Lua... Is not usually a problem other scripting languages, Lua does not use regular... Pattern describes on what to actually get back a string and the number of matches that.... Take an input string and the number of matches that occurred any character, there are also restrictive. The class % d matches any digit Skriptsprache Lua uwe Berger Beruf: Freizeit. Usually a problem all Time Highs: Talking crypto with Li Ouyang or trailing characters allowed! ),. Classes follow the same rules as other strings formatted version of its number... ( no preceeding or trailing characters allowed! ) you can circumvent this limitation some... ) provides advanced tools for searching and replacing recurring patterns in Rust more information about Lua patterns be... ' matches zero or more occurrences of characters of the string is returned erfolgen mit dem print... Will always get the longest sequence, it will match to the lua string patterns feature! That use patterns ( what some people mistakenly call regexes ) its first argument, the total number matches. To actually get back for char in ( `` '' ): gmatch `` ''. +´ modifier matches one or more spaces the end of the string is returned the of... So-Called format string follow the lua string patterns locale set for Lua pages, or 16... Be done for any non-magic characters by simply using them literally in a Lua function like string.match ( ) use. Functions that work with patterns, also called ( a subset of ) regular expressions, since there no.

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