组可能不存在的正则表达式模式

Question

我有一个 RegEx 模式需要匹配以下任何一行：

10-10-15 15:16:41.1 Some Text here 
10-10-15 15:16:41.12 Some Text here 
10-10-15 15:16:41.123 Some Text here 
10-10-15 15:16:41 Some Text here 

我可以用下面的模式匹配前 3 个：

(?<date>(?<day>\d{1,2})-(?<month>\d{1,2})-(?<year>(?:\d{4}|\d{2}))\s(?<time>(?<hour>\d{2}):(?<minutes>\d{2}):(?<seconds>\d{2})\.(?<milli>\d{0,3})))\s(?<Line>.*)

我如何匹配这一行（此处为 10-10-15 15:16:41 Some Text），它没有毫秒但仍将组返回到我的结果中，无论是空白值还是值为 0？

谢谢

正如我所说，下面的每一行都会匹配：

10-10-15 15:16:41.123 Some text Here
10-10-15 15:16:41.12 Some Text here 
10-10-15 15:16:41.1 Some Text here 
10-10-15 15:16:41. Some Text here 

这些组看起来像这样：

date    [0-18]  `10-10-15 15:16:41.`
day     [0-2]   `10`
month   [3-5]   `10`
year    [6-8]   `15`
time    [9-18]  `15:16:41.`
hour    [9-11]  `15`
minutes [12-14] `16`
seconds [15-17] `41`
milli   [18-18] ``
Line    [19-34] `Some Text here `

Answer 1

将毫秒设为可选?

/^([\d]{2})-([\d]{2})-([\d]{2}|[\d]{4})\s+([\d]{2}):([\d]{2}):([\d]{2})\.?(\d+)?\s+(.*?)$/

---

例子：

<?php

$strings = <<< LOL
10-10-15 15:16:41.1 Some Text here 
10-10-15 15:16:41.12 Some Text here 
10-10-15 15:16:41.123 Some Text here 
10-10-15 15:16:41 Some Text here 
LOL;

preg_match_all('/^([\d]{2})-([\d]{2})-([\d]{2}|[\d]{4})\s+([\d]{2}):([\d]{2}):([\d]{2})\.?(\d+)?\s+(.*?)$/m', $strings , $matches, PREG_PATTERN_ORDER);
for ($i = 0; $i < count($matches[0]); $i++) {

    $day = $matches[1][$i];
    $month = $matches[2][$i];
    $year = $matches[3][$i];
    $hours = $matches[4][$i];
    $minutes = $matches[5][$i];
    $seconds = $matches[6][$i];
    $ms = $matches[7][$i];
    $text = $matches[8][$i];


    echo "$day $month $year $hours $minutes $seconds $ms $text \n";
}

---

正则表达式演示：

https://regex101.com/r/aF9wN6/1

---

PHP 演示：

http://ideone.com/1aEt2E

---

正则表达式解释：

^([\d]{2})-([\d]{2})-([\d]{2}|[\d]{4})\s+([\d]{2}):([\d]{2}):([\d]{2})\.?(\d+)?\s+(.*?)$

Assert position at the beginning of a line (at beginning of the string or after a line break character) (line feed) «^»
Match the regex below and capture its match into backreference number 1 «([\d]{2})»
   Match a single character that is a “digit” (any decimal number in any Unicode script) «[\d]{2}»
      Exactly 2 times «{2}»
Match the character “-” literally «-»
Match the regex below and capture its match into backreference number 2 «([\d]{2})»
   Match a single character that is a “digit” (any decimal number in any Unicode script) «[\d]{2}»
      Exactly 2 times «{2}»
Match the character “-” literally «-»
Match the regex below and capture its match into backreference number 3 «([\d]{2}|[\d]{4})»
   Match this alternative (attempting the next alternative only if this one fails) «[\d]{2}»
      Match a single character that is a “digit” (any decimal number in any Unicode script) «[\d]{2}»
         Exactly 2 times «{2}»
   Or match this alternative (the entire group fails if this one fails to match) «[\d]{4}»
      Match a single character that is a “digit” (any decimal number in any Unicode script) «[\d]{4}»
         Exactly 4 times «{4}»
Match a single character that is a “whitespace character” (any Unicode separator, tab, line feed, carriage return, form feed) «\s+»
   Between one and unlimited times, as many times as possible, giving back as needed (greedy) «+»
Match the regex below and capture its match into backreference number 4 «([\d]{2})»
   Match a single character that is a “digit” (any decimal number in any Unicode script) «[\d]{2}»
      Exactly 2 times «{2}»
Match the character “:” literally «:»
Match the regex below and capture its match into backreference number 5 «([\d]{2})»
   Match a single character that is a “digit” (any decimal number in any Unicode script) «[\d]{2}»
      Exactly 2 times «{2}»
Match the character “:” literally «:»
Match the regex below and capture its match into backreference number 6 «([\d]{2})»
   Match a single character that is a “digit” (any decimal number in any Unicode script) «[\d]{2}»
      Exactly 2 times «{2}»
Match the character “.” literally «\.?»
   Between zero and one times, as many times as possible, giving back as needed (greedy) «?»
Match the regex below and capture its match into backreference number 7 «(\d+)?»
   Between zero and one times, as many times as possible, giving back as needed (greedy) «?»
   Match a single character that is a “digit” (any decimal number in any Unicode script) «\d+»
      Between one and unlimited times, as many times as possible, giving back as needed (greedy) «+»
Match a single character that is a “whitespace character” (any Unicode separator, tab, line feed, carriage return, form feed) «\s+»
   Between one and unlimited times, as many times as possible, giving back as needed (greedy) «+»
Match the regex below and capture its match into backreference number 8 «(.*?)»
   Match any single character that is NOT a line break character (line feed) «.*?»
      Between zero and unlimited times, as few times as possible, expanding as needed (lazy) «*?»
Assert position at the end of a line (at the end of the string or before a line break character) (line feed) «$»

Answer 2

^(\d+)-(\d+)-(\d+)\s(\d+):(\d+):(\d+)\.?(\d*)([a-zA-Z\s]+)

注意(\d*)，即使为空也会返回组。

Demo

Answer 3

解决了。我需要以下模式：

(?<date>(?<day>\d{1,2})-(?<month>\d{1,2})-(?<year>(?:\d{4}|\d{2}))\s(?<time>(?<hour>\d{2}):(?<minutes>\d{2}):(?<seconds>\d{2})(?<milli>\.?\d{0,3})))\s(?<logEntry>.*)

Answer 4

您可以使用以下（您的正则表达式稍作修改的版本）：

(?<date>(?<day>\d{1,2})-(?<month>\d{1,2})-(?<year>(?:\d{4}|\d{2}))\s(?<time>(?<hour>\d{2}):(?<minutes>\d{2}):(?<seconds>\d{2})(?<milli>\.\d{0,3})?))\s(?<logEntry>.*)

见DEMO

解释：

• 使<milli> 部分可选.. 而不是.，因为它也匹配像10-10-15 15:16:41123 Some Text here 这样的字符串..