使用正则表达式拆分字符串似乎不如预期的那样工作。

huangapple
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英文:

Spliting Strings by regex seems not to work as expected

问题

在PowerShell中有一个函数：

  1. function WriteToLog {
  2.     [CmdletBinding()]
  3.     param(
  4.         [Parameter(Mandatory, ValueFromPipeline)]
  5.         [AllowEmptyCollection()]
  6.         [AllowEmptyString()]
  7.         [string[]]$Message
  8.     )
  9.     BEGIN {}
  10.     PROCESS {
  11.         if ($Null -ne $Message) {
  12.             $dt = (Get-Date).ToString("yyyy-MM-dd HH:mm:ss")
  13.             foreach ($item in $Message) {
  14.                 if ($item.length -gt 0) {
  15.                     $it = $item -split '(.{1,70})' | Where-Object {$_}
  16.                     $dt + ": " + $it[0] | Write-Host
  17.                     $dt = $dt -replace '(.)',' '
  18.                     $i = 1
  19.                     while ($it[$i]) {
  20.                         $dt + "  " + $it[$i] | Write-Host
  21.                         $i++
  22.                     }
  23.                 }
  24.             }
  25.         }
  26.     }
  27.     END {}
  28. }

现在使用字符串调用它：

  1. "----" | WriteToLog

输出：

  1. 2023-05-25 00:28:05: -
  2.                      -
  3.                      -
  4.                      -
  5.                      -

我希望的是：

  1. 2023-05-25 00:28:05: -----

而不是将字符串拆分成字符。
如果字符串长度超过70个字符，它会按预期工作：

  1. "--------------------------------------------------------------------------" | WriteToLog

输出：

  1. 2023-05-25 00:32:37: ----------------------------------------------------------------------
  2.                      ----

有任何想法为什么会这样？

英文:

Having a function in PowerShell:

  1. function WriteToLog {
  2.     [CmdletBinding()]
  3.     param(
  4.         [Parameter(Mandatory, ValueFromPipeline)]
  5.         [AllowEmptyCollection()]
  6.         [AllowEmptyString()]
  7.         [string[]]$Message
  8.     )
  9.     BEGIN {}
  10.     PROCESS {
  11.         if ($Null -ne $Message) {
  12.             $dt = (Get-Date).ToString("yyyy-MM-dd HH:mm:ss")
  13.             foreach ($item in $Message) {
  14.                 if ($item.length -gt 0) {
  15.                     $it = $item -split '(.{1,70})' | Where-Object {$_}
  16.                     $dt + ": " + $it[0] | Write-Host
  17.                     $dt = $dt -replace '(.)',' '
  18.                     $i = 1
  19.                     while ($it[$i]) {
  20.                         $dt + "  " + $it[$i] | Write-Host
  21.                         $i++
  22.                     }
  23.                 }
  24.             }
  25.         }
  26.     }
  27.     END {}
  28. }

Now calling it with a string:

  1. "----" | WriteToLog

gives:

  1. 2023-05-25 00:28:05: -
  2.                      -
  3.                      -
  4.                      -
  5.                      -

I'd expected:

  1. 2023-05-25 00:28:05: -----

Not splitting the string in characters.
With a string longer than 70 characters it works as expected:

  1. "--------------------------------------------------------------------------" | WriteToLog

gives:

  1. 2023-05-25 00:32:37: ----------------------------------------------------------------------
  2.                      ----

Any idea why this happens?

答案1

得分: 1

将您的正则表达式更改为 '(?<=\G.{70})'，这样只有在字符计数为 70 时才会拆分，还使用了正向回顾与 \G，消除了过滤非空字符串的需要 (Where-Object { $_ })。另外，条件 if ($Null -ne $Message) 是不必要的，您已经在枚举集合并检查 if ($item.Length -gt 0)。

  1. function WriteToLog {
  2.     [CmdletBinding()]
  3.     param(
  4.         [Parameter(Mandatory, ValueFromPipeline)]
  5.         [AllowEmptyCollection()]
  6.         [AllowEmptyString()]
  7.         [string[]] $Message
  8.     )
  10.     process {
  11.         $dt = (Get-Date).ToString('yyyy-MM-dd HH:mm:ss')
  12.         foreach ($item in $Message) {
  13.             if ($item.Length -gt 0) {
  14.                 $it = $item -split '(?<=\G.{70})'
  15.                 $dt + ': ' + $it[0] | Write-Host
  16.                 $dt = [string]::new(' ', $dt.Length)
  17.                 for($i = 1; $i -lt $it.Length; $i++) {
  18.                     $dt + '  ' + $it[$i] | Write-Host
  19.                 }
  20.             }
  21.         }
  22.     }
  23. }
  25. '---------------------------------------------------------------------------' | WriteToLog
  26. '-----' | WriteToLog
  27. WriteToLog '', ''
英文:

Change your regex to &#39;(?&lt;=\G.{70})&#39; so it only splits if the char count is 70, also using a positive lookbehind with \G removes the need to filter where the token is not an empty string (Where-Object { $_ }). Also the condition if ($Null -ne $Message) is unnecessary, you're already enumerating the collection and checking if ($item.Length -gt 0).

  1. function WriteToLog {
  2.     [CmdletBinding()]
  3.     param(
  4.         [Parameter(Mandatory, ValueFromPipeline)]
  5.         [AllowEmptyCollection()]
  6.         [AllowEmptyString()]
  7.         [string[]] $Message
  8.     )
  10.     process {
  11.         $dt = (Get-Date).ToString(&#39;yyyy-MM-dd HH:mm:ss&#39;)
  12.         foreach ($item in $Message) {
  13.             if ($item.Length -gt 0) {
  14.                 $it = $item -split &#39;(?&lt;=\G.{70})&#39;
  15.                 $dt + &#39;: &#39; + $it[0] | Write-Host
  16.                 $dt = [string]::new(&#39; &#39;, $dt.Length)
  17.                 for($i = 1; $i -lt $it.Length; $i++) {
  18.                     $dt + &#39;  &#39; + $it[$i] | Write-Host
  19.                 }
  20.             }
  21.         }
  22.     }
  23. }
  25. &#39;---------------------------------------------------------------------------&#39; | WriteToLog
  26. &#39;-----&#39; | WriteToLog
  27. WriteToLog &#39;&#39;, &#39;&#39;

huangapple
  • 本文由 发表于 2023年5月25日 06:39:20
  • 转载请务必保留本文链接：https://go.coder-hub.com/76327822.html
  • powershell
  • regex
  • split
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