ngx.re.find ----------- **语法:** *from, to, err = ngx.re.find(subject, regex, options?, ctx?, nth?)* **环境:** *init_worker_by_lua*\**, set_by_lua*\**, rewrite_by_lua*\**, access_by_lua*\**, content_by_lua*\**, header_filter_by_lua*\**, body_filter_by_lua*\**, log_by_lua*\**, ngx.timer.*\* 与 [ngx.re.match](#ngxrematch) 类似但只返回匹配结果子字符串的开始索引 (`from`) 和结束索引 (`to`)。返回的索引值是基于 1 的，可以直接被用于 Lua 的 [string.sub](http://www.lua.org/manual/5.1/manual.html#pdf-string.sub) API 函数来获取匹配结果子串。 当出现任何错误时 (例如错误的正则表达式或任何 PCRE 运行时错误)，这个 API 函数返回两个 `nil` 以及一个描述错误的的字符串。 如果匹配不成功，此函数返回一个 `nil` 值。 下面是一个示例： ```lua local s = "hello, 1234" local from, to, err = ngx.re.find(s, "([0-9]+)", "jo") if from then ngx.say("from: ", from) ngx.say("to: ", to) ngx.say("matched: ", string.sub(s, from, to)) else if err then ngx.say("error: ", err) return end ngx.say("not matched!") end ``` 此示例将输出 from: 8 to: 11 matched: 1234 因为此 API 函数并不创建任何新 Lua 字符串或 Lua 表，运行速度大大快于 [ngx.re.match](#ngxrematch)。所以如果可能请尽量使用本函数。 自 `0.9.3` 版本开始，添加第 5 个可选参数 `nth`，用来指定第几个子匹配结果索引被返回。当 `nth` 为 0 (默认值) 时，返回完整匹配子串索引；当 `nth` 为 1 时，第一个(括号内的)子匹配结果索引被返回； 当 `nth` 为 2 时，第二个子匹配结果索引被返回，以此类推。当被指定的子匹配没有结果时，返回 `nil`。下面是一个例子： ```lua local str = "hello, 1234" local from, to = ngx.re.find(str, "([0-9])([0-9]+)", "jo", nil, 2) if from then ngx.say("matched 2nd submatch: ", string.sub(str, from, to)) -- yields "234" end ``` 此 API 函数自 `v0.9.2` 版开始提供。 > English source: **syntax:** *from, to, err = ngx.re.find(subject, regex, options?, ctx?, nth?)* **context:** *init_worker_by_lua*\**, set_by_lua*\**, rewrite_by_lua*\**, access_by_lua*\**, content_by_lua*\**, header_filter_by_lua*\**, body_filter_by_lua*\**, log_by_lua*\**, ngx.timer.*\* Similar to [ngx.re.match](#ngxrematch) but only returns the begining index (`from`) and end index (`to`) of the matched substring. The returned indexes are 1-based and can be fed directly into the [string.sub](http://www.lua.org/manual/5.1/manual.html#pdf-string.sub) API function to obtain the matched substring. In case of errors (like bad regexes or any PCRE runtime errors), this API function returns two `nil` values followed by a string describing the error. If no match is found, this function just returns a `nil` value. Below is an example: ```lua local s = "hello, 1234" local from, to, err = ngx.re.find(s, "([0-9]+)", "jo") if from then ngx.say("from: ", from) ngx.say("to: ", to) ngx.say("matched: ", string.sub(s, from, to)) else if err then ngx.say("error: ", err) return end ngx.say("not matched!") end ``` This example produces the output from: 8 to: 11 matched: 1234 Because this API function does not create new Lua strings nor new Lua tables, it is much faster than [ngx.re.match](#ngxrematch). It should be used wherever possible. Since the `0.9.3` release, an optional 5th argument, `nth`, is supported to specify which (submatch) capture's indexes to return. When `nth` is 0 (which is the default), the indexes for the whole matched substring is returned; when `nth` is 1, then the 1st submatch capture's indexes are returned; when `nth` is 2, then the 2nd submatch capture is returned, and so on. When the specified submatch does not have a match, then two `nil` values will be returned. Below is an example for this: ```lua local str = "hello, 1234" local from, to = ngx.re.find(str, "([0-9])([0-9]+)", "jo", nil, 2) if from then ngx.say("matched 2nd submatch: ", string.sub(str, from, to)) -- yields "234" end ``` This API function was first introduced in the `v0.9.2` release. [返回目录](#nginx-api-for-lua)