Powershell - F5 iRules -- 提取 iRules

Question

我收到了一个 F5 负载均衡器的配置文件，并被要求使用 PowerShell 对其进行解析，以便它为找到的每个 iRule 创建一个 .txt 文件。我对解析很陌生，我似乎无法理解它。

我设法提取了每条规则的名称并创建了一个单独的 .txt 文件，但我无法将规则的内容写入其中。由于并非所有规则都相同，我似乎无法使用正则表达式。

从配置文件中提取：

ltm rule /Common/irule_name1 {
SOME CONTENT
}

ltm rule /Common/irule_name2 {
SOME OTHER CONTENT
}

我现在有什么

$infile = "F5\config_F5"

$ruleslist = Get-Content $infile

foreach($cursor in $ruleslist)
{
if($cursor -like "*ltm rule /*") #new object started
{
    #reset all variables to be sure
    $content=""

    #get rulenames
    $rulenameString = $cursor.SubString(17)
    $rulename = $rulenameString.Substring(0, $rulenameString.Length -2)
    $outfile = $rulename + ".irule"

    Write-Host $outfile
    Write-Host "END Rule"
    #$content | Out-File -FilePath "F5/irules/" + $outfile
}
}

如何让我的 powershell 脚本读出每条规则括号之间的内容？ （在本例中为“某些内容”和“某些其他内容”）

Answer 1

通常解析涉及将特定输入（“字符串”）转换为 PowerShell 可以理解的“对象”（例如 HTML、JSON、XML 等），并通过“打点”遍历每个对象。

如果您无法将其转换为任何已知格式（我不熟悉 F5 配置文件...），并且只需要找出大括号之间的内容，您可以使用以下代码。

请注意，仅当您无法找到任何其他替代方案时才应使用此代码，因为这仅在使用的源文件代码正确时才有效，否则可能无法为您提供预期的输出。

# You can Get-Content FileName as well.
$string = @'
ltm rule /Common/irule_name1 {
SOME CONTENT
}

ltm rule /Common/irule_name2 {
SOME OTHER CONTENT
}
'@

function fcn-get-content {
    Param (
        [ Parameter( Mandatory = $true ) ]
        $START,
        [ Parameter( Mandatory = $true ) ]
        $END,
        [ Parameter( Mandatory = $true ) ]
        $STRING
    )
    $found_content    = $string[ ( $START + 1 ) .. ( $END - 1 ) ]
    $complete_content = $found_content -join ""
    return $complete_content
}

for( $i = 0; $i -lt $string.Length; $i++ ) {
#   Find opening brace
    if( $string[ $i ] -eq '{' ) {
        $start = $i
    }
#   Find ending brace
    elseif( $string[ $i ] -eq '}' ) {
        $end = $i
        fcn-get-content -START $start -END $end -STRING $string
    }
}

为了让所有内容都包含在大括号中（甚至是嵌套大括号）：

$string | Select-String '[^{\}]+(?=})' -AllMatches | % { $_.Matches } | % { $_.Value }

Answer 2

要解析具有灵活结构的数据，可以使用状态机。也就是逐行读取数据，保存你所处的状态。这是规则的开始吗？实际规则？统治结束？通过了解当前状态，可以对数据执行操作。像这样，

# Sample data
$data = @()
$data += "ltm rule /Common/irule_name1 {"
$data += "SOME CONTENT"
$data += "}"
$data += "ltm rule /Common/irule_withLongName2 {"
$data += "SOME OTHER CONTENT"
$data += "SOME OTHER CONTENT2"
$data += "}"
$data += ""
$data += "ltm rule /Common/irule_name3 {"
$data += "SOME DIFFERENT CONTENT"
$data += "{"
$data += "WELL,"
$data += "THIS ESCALATED QUICKLY"
$data += "}"
$data += "}"

# enum is used for state tracking
enum rulestate {
start
stop
content
}

# hashtable for results
$ht = @{}

# counter for nested rules
$nestedItems = 0

# Loop through data
foreach($l in $data){

    # skip empty lines
    if([string]::isNullOrEmpty($l)){ continue }

    # Pick the right state and keep count of nested constructs
    if($l -match "^ltm rule (/.+)\{") {
        # Start new rule
        $state = [rulestate]::start
    } else {
        # Process rule contents

        if($l -match "^\s*\{") {
            # nested construct found
            $state = [rulestate]::content
            ++$nestedItems
        } elseif ($l -match "^\s*\}") {
            # closing bracket. Is it
            # a) closing nested
            if($nestedItems -gt 0) {
                $state = [rulestate]::content
                --$nestedItems
            } else {
                # b) closing rule
                $state = [rulestate]::stop
            }
        } else {
            # ordinary rule data
            $state = [rulestate]::content
        }
    }

    # Handle rule contents based on state
    switch($state){
        start {
            $currentRule = $matches[1].trim()
            $ruledata = @()
            break
        }
        content {
            $ruledata += $l
            break
        }
        stop {
            $ht.add($currentRule, $ruledata)
            break
        }
        default { write-host "oops! $state" }
    }

    write-host "$state => $l"
}

$ht

输出规则

SOME CONTENT

SOME OTHER CONTENT
SOME OTHER CONTENT2

SOME DIFFERENT CONTENT
{
WELL,
THIS ESCALATED QUICKLY
}