|
string.gsub 函數(shù)有三個(gè)參數(shù)：目標(biāo)串,，模式串,，替換串,。 基本作用是用來查找匹配模式的串,，并將使用替換串其替換掉： s = string.gsub("Lua is good", "good", "bad?") print(s) --> Lua is bad string.gsub 的第二個(gè)返回值表示進(jìn)行替換操作的次數(shù)。例如,， 下面代碼計(jì)字符串中空格出現(xiàn)的次數(shù)： _, count = string.gsub("test test", " ", " ") _ 表示啞元變量 模式串 . 任意字符 %a 字母 %c 控制字符 %d 數(shù)字 %l 小寫字母 %p 標(biāo)點(diǎn)字符 %s 空白符 %u 大寫字母 %w 字母和數(shù)字 %x 十六進(jìn)制數(shù)字 %z 代表 0的字符 特殊字符如下： (). % + - * ? [ ^ $ % 也作為以上特殊字符的轉(zhuǎn)義字符,。 [] 該方框作為匹配該范圍的集合，,。 如[0-9] 則匹配0到9的數(shù)字范圍 Lua 中的模式修飾符有四個(gè)： + 匹配前一字符 1 次或多次,，最長(zhǎng)匹配 * 匹配前一字符 0 次或多次，最長(zhǎng)匹配 - 匹配前一字符 0 次或多次,，最短匹配 匹配前一字符 0 次或 1次 '+',，匹配一個(gè)或多個(gè)字符，總是進(jìn)行最長(zhǎng)的匹配,。 如,，模式 '%a+' 匹配一個(gè)或多個(gè)字母或者一個(gè)單詞： 注意以上的區(qū)別： 如：匹配c中的注釋串 用 '/%*.*%*/' 和'/%*.-%*/' str = "int x; /* x */ int y; /* y */" print(string.gsub(str, "/%*.*%*/", "<注釋串>")) --> int x; <注釋串> 采用 '.-' 則為最短匹配，即匹配 "/*" 開始到第一個(gè) "*/" 之前的部分： str = "int x; /* x */ int y; /* y */" print(string.gsub(str, "/%*.-%*/", "<注釋部分>")) --> int x; <注釋串> int y; <注釋串> 以 '^' 開頭表示只匹配目標(biāo)串的開始部分,， 以 '$' 結(jié)尾表示只匹配目標(biāo)串的結(jié)尾部分,。 %b 表示匹配對(duì)稱字符，注意其只能針對(duì)的ansi碼單字符,。 x = string.gsub("xdddddyxxx", "%bxy", "取代") print(x) -->取代xxx 如去除字符串首尾的空格： function trim (s) return (string.gsub(s, "^%s*(.-)%s*$", "%1")) end --------------------------------- 看原文中的gsub注釋：相當(dāng)詳細(xì),，不過對(duì)于模式解釋補(bǔ)充在上。 string.gsub (s, pattern, repl [, n]) Returns a copy of s in which all occurrences of the pattern have been replaced by a replacement string specified by repl, which may be a string, a table, or a function. gsub also returns, as its second value, the total number of substitutions made. repl是字符串,，則為替換,。 如果在參數(shù)前有%則表示符合匹配的字符串 If repl is a string, then its value is used for replacement. The character % works as an escape character: any sequence in repl of the form %n, with n between 1 and 9, stands for the value of the n-th captured substring (see below). The sequence %0 stands for the whole match. The sequence %% stands for a single %. repl作為表參數(shù) If repl is a table, then the table is queried for every match, using the first capture as the key; if the pattern specifies no captures, then the whole match is used as the key. 如果參數(shù)為函數(shù)，則每次匹配成功則調(diào)用該函數(shù) If repl is a function, then this function is called every time a match occurs, with all captured substrings passed as arguments, in order; if the pattern specifies no captures, then the whole match is passed as a sole argument. If the value returned by the table query or by the function call is a string or a number, then it is used as the replacement string; otherwise, if it is false or nil, then there is no replacement (that is, the original match is kept in the string). 參數(shù)n則限制最大 The optional last parameter n limits the maximum number of substitutions to occur. 舉例： %1 表示符合模式的第一個(gè)匹配 x = string.gsub("hello world", "(%w+)", "%1 %1") --> x="hello hello world world" 第4項(xiàng) x = string.gsub("hello world", "%w+", "%0 %0", 1) --> x="hello hello world" hello 和from作為模式中左匹配為%1,，world 和lua為右匹配,，為%2 x = string.gsub("hello world from Lua", "(%w+)%s*(%w+)", "%2 %1") --> x="world hello Lua from" 替換 以$打頭的字符串 x = string.gsub("home = $HOME, user = $USER", "%$(%w+)", os.getenv) --> x="home = /home/roberto, user = roberto" 參數(shù)為函數(shù)類型 x = string.gsub("4+5 = $return 4+5$", "%$(.-)%$", function (s) return loadstring(s)() end) --> x="4+5 = 9" 參數(shù)為表類型 local t = {name="lua", version="5.1"} x = string.gsub("$name-$version.tar.gz", "%$(%w+)", t) --> x="lua-5.1.tar.gz" ============================== gmatch 的用法： 在模式符合匹配多次時(shí) 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. 看例子： s = "hello world from Lua" for w in string.gmatch(s, "%a+") do print(w) end 采用gmatch來解析到表類型 t = {} s = "from=world, to=Lua" for k, v in string.gmatch(s, "(%w+)=(%w+)") do t[k] = v end 一個(gè)http傳送參數(shù)的應(yīng)用 URL 編碼, 這種編碼將一些特殊字符（比 '=' '&' '+'）轉(zhuǎn)換為"%XX"形式的編碼， XX是字符的16進(jìn)制表示,，空白為'+',。 如，將"a+b = c" 編碼為 "a%2Bb+%3D+c" 一個(gè)典型的參數(shù)串： name=al&query=a%2Bb+%3D+c&q=yes+or+no 1先把空格和16進(jìn)制編碼轉(zhuǎn)換為ansi碼 function convet1(s) s = string.gsub(s, "+", " ") s = string.gsub(s, "%%(%x%x)", function (h) return string.char(tonumber(h, 16)) end) return s end 2.解析參數(shù)串 p = {} function decode (s) for name, value in string.gmatch(s, "([^&=]+)=([^&=]+)") do name = unescape(name) value = unescape(value) p[name] = value end end |
|
|
