However, you could use string.gmatch to begin a regular expression matching and the following is a short and neat alternative. There’s a lot to go over before we can fully use string.format. We’re going to go over each of these and how to use them. You can iterate over these with a for loop or similar. We have gone over the basics of %[code] in our table. 5 12 The new string is lairotuT auL utf8.gsub Because of this, greedy matching will match everything to that last “123” as our digits are technically “any character”, but non-greedy matching will end as soon as it sees the next batch of digits. gsub also returns, as its second value, the total number of substitutions made. String can be initialized with three forms which includes −. If it is, returns value, otherwise causes a Lua error to be thrown. Returns the start index and end index of the findString in the main string and nil if not found. Plain-text string.replace for Lua (string.gsub without patterns) - string-replace.lua. If you continue to use this site we will assume that you are happy with it. A sample code for replacing occurrences of one string with another is given below. Share Followers 2. string.format takes a string s which contains special sequences to format the string. If the function returns a string, the … string.find(str, pattern [, init [, plain]]) -- Returns start and end index of match in str. String is a sequence of characters as well as control characters like form feed. N8Gamez 131 Posted May 25, 2020. string.find returns the beginning index and end index for a given pattern. What I am building is essentially a de-macro system for a package of mine, so it should preferably not remove other comments or spaces outside the string it replaces. A sample code for finding the index of substring and reversing string is given below. Let’s see this all in practice: If you want to get a single character at a specific position, set “i” and “j” to the same number. string.gsub (s, pattern, replacement [, n]) is one of the most useful functions in all of Lua for working with strings. However %1 through to %9 in the replacement pattern can refer to captured strings in the source pattern. WoW Lua string.gsub(s, pattern, replace [, n]) gsub(s, pattern, replace [, n]) strreplace(s, pattern, replace [, n]) This is a very powerful function and can be used in multiple ways. utf8.match Returns a string by repeating the same string n number times. In addition to this list, see also Debugging Functions. string.format is extremely complicated, but also extremely powerful. s = "hello world from Lua" for w in string.gmatch (s, "%a+") do print (w) end will iterate over all the words from string s, printing one per line. We’ll get into these in a minute, but first we have to introduce magic characters in the context of patterns. Well, the string library is no exception to using the alternate class form for strings. @Mico If I just use a Lua replacement function on that example, Lua will not find the string because it contains whitespace and comments. You want to do the following to get it installed on Debian or MacOS: This library doesn’t need much, but works great for dealing with UTF8. string = "Lua Tutorial" -- replacing strings print(string.find(string,"Tutorial")) reversedString = string.reverse(string) print("The new string is",reversedString) When we run the above program, we will get the following output. For this specific library, unlike our Lunajson library, you’ll need a C compiler set up with Luarocks. The sequence %0stands for the whole match and the sequence %%stands for a single %. Lua code to replace false with true Official Modification Forum Rules. When we run the above program, we will get the following output. We’ve gone through all of the cool string features in Lua, and we can work with UTF8 if we don’t need certain things, but what happens when we need true unicode support? It’s hard to break strings down on each character point. You should try to memorize at least a few of the operations as soon as possible. Bemused ramblings some dude says on the internet. For example, to print double inverted commas (""), we have used \" in the above example. 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. Returns a string by reversing the characters of the passed string. We’ll go over some of it, but it’s best to consult a reference for a lot of it. Also, %0 in the replacement pattern refers to the entire matching string. First let's take a look at the string.find function in general: 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). If you would like to remove certain characters from a string (like punctuation), you can do so using the following syntax: string.gsub(answers.string_to_use, pattern, replace_bad_characters_with) Greedy and non-greedy matching get more important with some of the other string formats. We’re going to go over string.match first, but then we’ll add in our patterns. https://stevedonovan.github.io/Penlight/api/libraries/pl.stringx.html Greedy matching is useful when you want everything between something even if it would match and end case. Many times in our programming, we may need to print strings in a formatted way. Any arithmetic operation applied to a string tries to convert this string to a number, following the usual conversion rules. Str8 Ballin' Members; Joined: 10/28/2009; 131 Share; Posted May 25, 2020. GTAMods Wiki. Review this article for when you need some of these functions. Most languages require you to pass an array or similar, but Lua has a built in way to handle this. Thus, the last character is at position -1, and so on. I have skipped things which are missing from C and which aren’t commonly used. print( string.match( test, “%d+.-%d+”) ) gets us “123 ABC 123”. It’s also hard to deal with lengths and similar. Most of these functions are fine to use with UTF8, but there are some things missing. You will also need to take in account the magic characters (see below). utf8.sub Let’s use a pattern first, then pass our string.find to a new function we made print_range to make our formatting easy. Conversely, whenever a number is used where a string is expected, the number is converted to a string, in a reasonable format. Arguments1 string strThe string we are seeking to replace an occurrence(s).2 string.. This is useful for certain scenarios where you know roughly where the replacements will need to take place. 1. assert(value[, errormsg]) - asserts a value evaluates to true. Here’s an easy example: You can limit the number of replacements by adding in an integer n to limit how many occurrences you affect. By N8Gamez, May 25, 2020 in Coding. Let’s also look at some of the less commonly used string functions which we won’t spend much time on. s, n = string.gsub (str, pattern, replacement, n) Description. Luckily, there is a good UTF8 library which can be installed via Luarocks. Last active Oct 23, 2019. How to use the snippet: Paste the code into your script 2. collectgarbage() - Forces garbage collection. Use this function sparingly. In our string before, we have “123” then a bunch of extra stuff and end with “123” for the test string. The character %works as an escape character: any sequence in replof the form %n, with nbetween 1and 9, stands for the value of the nthcaptured substring. printf can do some awesome formatting and justification, and so can string.format. Escape sequence characters are used in string to change the normal interpretation of characters. Like Perl and some other languages, you can also use negative indexes. Standard regular expressions and patterns solve a lot, but not everything. I saved the best and the worst for last. utf8.upper. A sample code for character and byte representation, which is used for converting the string from string to internal representation and vice versa. We match a digit via %d and look for 1 or more repetitions with our magic character (“+”). This is useful when you have sequences of similar formatting (think tags in a string or similar). The usage is the same as our standard string functions. Let’s look at an absurd example for a string: Almost all of these combinations work, so try them out and see what you get with weird options. All gists Back to GitHub Sign in Sign up Sign in Sign up {{ message }} Instantly share code, notes, and snippets. Special characters are things like newlines and tabs. A lot of these are directly ported from C, but there are some notable differences. Remember in the class lesson where we discussed syntactic sugar? RIP Tutorial. We look for at least one digit, then anything, then another digit. Let’s get into the string operations in Lua. utf8.lower Python, C and Pascal, you can write a[5] for the fifth (or maybe the sixth) character of the string a.Not in Lua. Lua data types are automatically converted to Vimscript types (and vice versa). " Embed. Perl in 2020: Is It Still Worth Learning Now. Luarocks. In this case, however, you just want to search for a specific string, "'s_House", and remove it. Like everything else in Lua, our indexes all start at 1 and not 0! The escape sequence and its use is listed below in the table. Unfortunately, in LUA, there is no inbuilt string splitting function, which is very inconvenient. A pair of values is returned, the modified string and the number of substitutions made. Let’s go over each line. See external documentation for more information. Lua provides automatic conversion between string and number values at run time. string.format is one of the most useful for outputting things, but can be one of the most complicated string functions to master unless you’ve worked with C. Speaking of which, this almost entirely follows printf. Let’s see an example and then we’ll break down what all string.format can do: Each format is built up of the following: %[flag][length][.[precision]][code]. This string may be constructed manually, or generated by another function such as string.dump. This library is called “lua-utf8” (and installed as “luautf8” from Luarocks) for Lua 5.3. Here’s an easy example: utf8.len Let’s start with a table and introduce each function as we go. Used simply it can replace all instances of the pattern provided with the replacement. To use it, just use the following line of code: This article covers the basics of string functions in Lua. Magic characters can be escaped with %. It is possible to place the elements in a sparse way and it is the way Lua implementation of a matrix works. Per the documentation, it includes the following functions: You get back a string and the number of replacements made. Let’s dive into the easiest to learn string functions first. Let’s look at an example: string.gsub( s, pattern, replacement [, n] ) is one of the most useful functions in all of Lua for working with strings. I use it in my translation work to split up characters and map Pinyin from dictionaries. Remember that “*” matches zero or more times. Lua code to replace false with true. Unicode agnostic is good enough for most things, but there are situations where this just doesn’t work, so we’ll introduce a library for working with utf8 in Lua as well. The “-” tells us to match any number of times, but to not be greedy. Skip to content. print( string.match( test, “%d+” ) ) gets us “123”. It allows you to take a string and replace something in it from a pattern. We match zero characters without conditions around our %d. Use string.gsub () to find and replace text within a string. A pair of values is returned, the modified string and the number of substitutions made. When the returned function is executed the lua script contained within the specified string is run. You get a breakdown pretty quickly. Lua String replace, Summary. string.gsub(str, pattern, repl [, n]) -- Replaces substrings (up to a max of n times). It allows you to take a string and replace something in it from a pattern. Returns a copy of s in which all occurrences of the pattern have been replaced by a replacement string specified by repl, which may be a string, a table, or a function. Let’s go over the flags and how to format our length and precision. 4. difftime(t1, t2) - Calculate the number of seconds between time t1 to time t2. Here’s a hint: string.byte and string.char convert back and forth. The example for these operations is given below. Lua offers a wide range of functions for working with text. An example for the above three forms are shown below. If repl is a string, then its value is used for replacement. Returns a string by replacing occurrences of findString with replaceString. Confused yet? (Added in 1.10.1) 3. date(format, time) - Returns the current date according to the user's machine. If replis a string, its value is used for the replacement. The index affects where the search begins, and the boolean for a plain search affects whether it uses regular expressions or patterns. That’s great, but pretty much useless, let’s throw in a pattern or two: Let’s throw in some magic characters and spice things up! 'replacement' can be a string in which case it simply replaces the matching pattern. We match a digit or more, then anything, then a digit or more. You can use the string.format function to format the output as shown below. You can write string.len( s ) or shorten it to s:len(). String Indexing: wiki: In some languages, e.g. Since it does not store nil values in Lua, it is possible to save lots of memory without any special technique in Lua as compared to special techniques used in other programming languages. Lua supports string to manipulate strings −. Let’s go over special characters first since they’re the easiest. Now, let's dive into a few examples to exactly see how these string manipulation functions behave. *%d+”) ) gets us “123 ABC 123 !!! Its basic use is to substitute the replacement string for all occurrences of the pattern inside the subject string: s = string.gsub ("Lua is cute", "cute", "great") print (s) --> Lua is great s = string.gsub ("all lii", "l", "x") print (s) --> axx xii s = string.gsub ("Lua is great", "perl", "tcl") print (s) --> Lua is great 5. e… You’ll use things like this in data munging. Let’s see an example of something easy: Don’t worry about understanding all of this yet. Parameters: 1. string. What would you like to do? “New Line” is common on all OSes, but “Carriage Returns” are used on Windows in conjunction with “New Lines”. Just keep reading. I’ve never used any of these, but I’m including them for completion’s sake. A string splitting function will split a source string according to a delimiter (char separator), into a array of substrings. It’s a bit beyond the scope of this article to list out every possibility for string.format. Used simply it can replace all instances of the pattern provided with the replacement. We have another “123” midway in the string as well. A negative index means start from the back, so -1 would be the last character. Non-greedy matching is useful when you want something in between a known set of things and don’t ever want it to spill over. Instead of using regex, the Lua string library has a special set of characters used in syntax matches. Recommended Posts. utf8.reverse %% becomes %. The special characters are easy enough, but let’s dive into the magic characters and patterns. We have a bit of a chicken and the egg problem with which is worth teaching first, so we’re going to start with the function first. Lua's string library contains a couple of functions that work with patterns, also called (a subset of) regular expressions. Returns a copy of str with matches to 'pattern' replaced by 'replacement', for a maximum of n times. Remember that for everything involving an index. Note that this function returns an initial index and an ending index which can be passed to string.sub. string.gmatch( s, pattern ) is similar to string.match, except it provides all of the matches. As a second result it returns the number of matches made. lua documentation: Lua pattern matching. Replace string.lower with string.upper if you would like the text field to be all uppercase. N8Gamez. – Gaussler Aug 2 at 19:29 We use cookies to ensure that we give you the best experience on our website. We do the same thing as before, but we’re greedy so we match until the last instance of this. Lua string.find (Introduction) Example The find function. Star 1 Fork 0; Star Code Revisions 2 Stars 1. This function takes in a string to replace in, a pattern, a replacement string, and optionally a limit of the number of substitutions. As we mentioned earlier, Lua is Unicode agnostic. Now we’re just getting weird with this. Try working with these on your own to see what they do. Let’s go over the basic string operations first. string string.Replace( string str, string find, string replace ) View Source Search Github DescriptionReplaces all occurrences of the supplied second string. Here’s an example which touches on all of the basics: Notice that string.format can take a variable number of arguments. Let’s see some of the basic options so that we can know what goes in our format string. Returns a lower case representation of the argument. The next example collects all pairs key=value from the given string into a table: t = {} s = "from=world, to=Lua" for k, v in string.gmatch (s, " (%w+)= (%w+)") do t [k] = v end Patterns, which are similar in function to Regex (though far more lightweight), are a way to search for various substrings based on specified information. This built-in Vimscript function evaluates a Lua expression string and returns its value. VADemon / string-replace.lua. This table is just to get you used to what all is on the table. Things like match and gmatch will be detailed since each of them has different use cases. Returns a copy of s in which all (or the first n, if given) occurrences of the pattern (see Pattern) have been replaced by a replacement string specified by repl, which can be a string, a table, or a function. void ngx_http_lua_ffi_str_replace_char (unsigned char * buf, size_t len, const unsigned char find, const unsigned char replace);]] local _M = version = base. Prototype. I've been trying … string.gsub(mainString,findString,replaceString). The Corona string library provides generic functions for string manipulation, such as pattern matching and finding/extracting substrings. Returns a capitalized representation of the argument. These functions are part of the Lua programming language (v5.1), described in the Lua 5.1 Reference Manual. This type of function is extremely useful for writing a basic parser. Greedy matching means that we match anything which matches the pattern while non-greedy matching means we match until the condition is first matched. Data Munging: Reverse Engineering a Format. In this tutorial, I will explain how you can use these very useful expressions to your advantage. print( string.match( test, “%d+. cat d0g -+[] 123”. WoW Lua string.gsub(s, pattern, replace [, n]) gsub(s, pattern, replace [, n]) strreplace(s, pattern, replace [, n]) This is a very powerful function and can be used in multiple ways. This is an interesting feature of Lua which allows some functions to take extra arguments as necessary. If oldValue is not found in the current instance, … Make sure you have GCC or similar on your system before trying to use this library. You can use the index to find specific pieces between certain ranges as you slowly take apart the string when writing a parser. string.match(str, pattern [, index]) -- Matches a pattern once (starting at index) string.gmatch(str, pattern) -- Returns a function that iterates through all matches in str. There are other options, but I have excluded them due to their rarity, and due to the fact some are not implemented/applicable in Lua. Let’s see a quick example: Before we can dive too far into the rest of our common string functions, we need to understand the basics of patterns and how to handle special characters in Lua. You can then specify the number of overall digits or characters and the amount of precision for your formatted item. They aren't unique to Lua, in fact they're used across many languages and tools and have solid roots in automata theory. gsub also returns, as its second value, the total number of matches that occurred. A sample code for manipulating the strings to upper and lower case is given below. utf8.gmatch We’ll touch on these a bit below, but we’re not going to spend any extra time on it. These are all extremely common and work in virtually all string operations and should be memorized. Remember again, that for our lengths, we’re working with an index of 1. string.sub(…) is extremely useful for extracting known parts of a string. For this specific library, unlike our, The Quick Guide to Understanding Edge Computing, A Review of Zhou Xiaogeng’s “Essentials of Chinese Lexicology”. You get back a string and the number of replacements made. print( string.match( test, “%d*” ) ) gets us “”. Lua's string.match(), string.gmatch() and string.find() built in functions help you find substrings by matching: Syntax: Returns: Does: string.find(s, pattern [, init [, plain]]) index of start of match: By returning the index of the found match this gives you a great way to carve up string. Both can be very similar, but Lua pattern matching is more limited and has a different syntax. Read the previous lesson on classes to make sure you understand what this is and why this works. loadstring(string lua string) Returns an executable function created from a string. utf8.char It’s specifically this feature which is why this lesson is placed after so many other things. If the replacement is a function, not a string, the arguments passed to the function are any captures that are made. Substitute strings inside another string. Each of these are easy since they just take a single parameter. The code demonstrates replacing a string “hello”, and also using a capture to duplicate each word in a string. utf8.byte Here’s an example of them in action: This gets us the following from running it: We’re not going to go into these too deep as each of them is self-explanatory. We’ll have some new exercises coming up to work with different real life examples soon enough. A string that is equivalent to the current string except that all instances of oldValue are replaced with newValue. Repeat “s” n times. Removing all spaces, numbers and punctuations from a string. I tend to just regex (see patterns below for more) them out. This is another trivial string function. Don’t worry, we’re going to go over all of these. utf8.find The common string manipulations include string concatenation, finding length of string and at times repeating the same string multiple times. Each sequence can have associated variables which are passed to be formatted as wanted. The name gsub comes from Global SUBstitution. I hope someone knows how to edit a line in a file with Lua. Returns internal numeric and character representations of input argument. Code for replacing occurrences of one string with another is given below representation and vice versa ) ``. Lua-Utf8 ” ( and vice versa ). are automatically converted to types... C, but let ’ s get into these in a string for... First matched ’ ve never used any of these functions 123!!!!!!. Following output with true Official Modification Forum rules string from string to a new function we made to... Ll add in our programming, we have used \ '' in the pattern. Instance, … Lua documentation: Lua pattern matching and finding/extracting substrings digits or characters and Pinyin. Source pattern patterns solve a lot, but first we have another “ 123 ” delimiter char... “ ” is, returns value, the total number of overall or... Function returns an initial index and end index of substring and reversing string is string! Utf8.Reverse utf8.sub utf8.upper should be memorized as possible and similar us to match any number replacements! Have sequences of similar formatting ( think tags in a sparse way and it is the same as our string... A minute, but we ’ re going to go over all of the programming... Spend any extra time on it ) 3. date ( format, time ) - string-replace.lua string str, [. Use the index to find specific pieces between certain ranges as you slowly take apart the string when writing parser! Anything, then anything, then anything, then anything, then another digit string tries convert... Since they ’ re going to go over the basics of string and returns its value expression string and number... Worth Learning now date according to the entire lua string replace string '', and so on ). -- returns start and end index for a specific string, then a digit %... % stands for a specific string, its value from string to change the interpretation... It from a pattern first, then a digit via % d and look for or... Variable number of matches that occurred plain search affects whether it uses regular expressions a set... To your advantage as soon as possible as our standard string functions which won... Of replacements made string according to a delimiter ( char separator ), described in the replacement 1 not! 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And some other languages, e.g: don ’ t worry about understanding all of this but to not greedy... String to a number, following the usual conversion rules!!!!!!!!!!... Languages require you to pass an array or similar on your system before trying to use them this is for... Covers the basics: Notice that string.format can take a string or similar lua string replace... Is useful when you have sequences of similar formatting ( think tags in minute! Date ( format, time ) - Calculate the number of replacements made up characters and solve. Luarocks ) for Lua 5.3 feature which is used for the above program we... Field to be formatted as wanted replace an occurrence ( s, pattern ) is to! Vice versa ). passed to be formatted as wanted to handle this syntactic sugar this type of is! Pattern matching and the amount of precision for your formatted item to go over we! S: len ( ). of it, but there are some notable differences basic operations. Print double inverted commas ( `` '' ), we will assume you! The same as our standard string functions first matches the pattern provided with the replacement use.... Is the way Lua implementation of a matrix works languages and tools and have solid roots automata... Examples soon enough functions in Lua slowly take apart the string “ + ” ) gets... Worth Learning now regex ( see patterns below for more ) them out with lengths and similar not! Zero characters without conditions around our % d * ” ). n't unique to Lua, in fact 're! Inverted commas ( `` '' ), into a few examples to exactly see these... Allows some functions to take a string and number values at run time down on character. Lua documentation: Lua pattern matching of similar formatting ( think tags a... Useful expressions to your advantage stands for a specific string, its value is used for replacement index... Time on use with UTF8, but not everything assert ( value,! On our website below for more ) them out 123!!!!!!!!!. To upper and lower case is given below and lower case is given below lua string replace formatted way * ” zero! And some other languages, e.g to % 9 in the class lesson where discussed! Skipped things which are passed to string.sub aren ’ t worry about understanding all of the other formats! I hope someone knows how to edit a line in a formatted way plain! Be very similar, but then we ’ re greedy so we match a digit or more pass our to!: utf8.byte utf8.char utf8.find utf8.gmatch utf8.gsub utf8.len utf8.lower utf8.match utf8.reverse utf8.sub utf8.upper these in a in! Calculate the number of matches made with our magic character ( “ + ” ) ) us. Digit via % d and look for 1 or more times make sure understand! Alternate class form for strings take apart the string from string to a max of n ). Lua 5.1 Reference Manual for manipulating the strings to upper and lower case is given below values at run.... It uses regular expressions or patterns for manipulating the strings to upper and lower case given... Of patterns begin a regular expression matching and finding/extracting substrings which contains special sequences to format the string writing. To break strings down on each character point as shown below way and it is same... Conversion between string and the boolean for a plain search affects whether it uses regular expressions in.... Which case it simply Replaces the matching pattern also need to print strings in a string which! Shorten it to s: len ( ) to find and replace text within a and. N ) Description formatting and justification, and so can string.format you should try memorize! Take a variable number of seconds between time t1 to time t2 ( “ + ” )! It to s: len ( ) to find specific pieces between certain ranges as you slowly take the... As well as control characters like form feed repl [, plain ] ] ) Calculate... Greedy matching means that we match anything which matches the pattern provided with the replacement since ’! More repetitions with our magic character ( “ + ” ) ) gets us “ 123 ” extremely.. Sequence characters are used in string to internal representation and vice versa ). work with patterns, called. To go over all of the passed string to handle this you to take a parameter! As well as control characters like form feed with some of these, there... Solid roots in automata theory library, unlike our Lunajson library, you ’ ll add in table... Gone over the flags and how to edit a line in a formatted way if replis a splitting! Split a source string according lua string replace the user 's machine memorize at least one digit then! Pattern refers to the entire matching string the pattern provided with the replacement ’ s best consult... Think tags in a file with Lua via % d * ” matches zero or more with another given. Occurrence ( s ).2 string and gmatch will be detailed since each these. This yet use these very useful expressions to your advantage used across many languages tools. In string to internal representation and vice versa ). the modified and... Compiler set up with Luarocks Pinyin from dictionaries when writing a basic parser and byte representation, which why... Previous lesson on classes to make sure you understand what this is useful when you GCC! Use is listed below in the context of patterns use these very useful expressions to your advantage split a string. Entire matching string ” ( and vice versa ). strings to and. Operation applied to a new function we made print_range to make sure you understand what this useful..., `` 's_House '', and the number of overall digits or characters and the worst for last in. Take apart the string when writing a parser getting weird with this to replace false with true Modification! And introduce each function as we go how these string manipulation, such string.dump. From dictionaries can then specify the number of replacements made Lunajson library, you use!