如何在PowerShell中基于单个属性使用Compare-Object并输出全部属性

问题背景 #

现有包含MD5哈希值、文件名（含文件大小和时间戳）的日志文件：

hashlog1.log： #

2E331B30A705D462541398874451A955 \steamapps\appmanifest_1036890.acf 798 20230919_003055
D9A3D74B9F48CC599406F1D74D293261 \steamapps\appmanifest_1046030.acf 795 20231021_213325
2C364B22B4866903ED5E3BD9740B9DFA \steamapps\appmanifest_1086410.acf 762 20230413_034326
88D100F2A7FFC2C912B59B45AED9DC48 \steamapps\appmanifest_1091500.acf 925 20231026_112000
2A03A13E570CDA7424216DEF84C958EA \steamapps\appmanifest_1151640.acf 901 20230512_235832

hashlog2.log： #

97CAF30C2E1F73ED121F75D947DB29C3 \steamapps\appmanifest_1036890.acf 798 20231122_123455
D9A3D74B9F48CC599406F1D74D293261 \steamapps\appmanifest_1046030.acf 795 20231021_213325
2C364B22B4866903ED5E3BD9740B9DFA \steamapps\appmanifest_1086410.acf 762 20230413_034326
78CF976F8BA64DAF19319E84B8133598 \steamapps\appmanifest_1091500.acf 687 20231122_125522
2A03A13E570CDA7424216DEF84C958EA \steamapps\appmanifest_1151640.acf 901 20230512_235832

通过以下代码生成带列头的对象集合：

$file1=(Get-Content -Path "hashlog1.log") | Select @{N='Hash'; E={($_ -split ' ',2)[0]}},@{N='File'; E={(($_ -split ' ',2)[1])}}
$file2=(Get-Content -Path "hashlog2.log") | Select @{N='Hash'; E={($_ -split ' ',2)[0]}},@{N='File'; E={(($_ -split ' ',2)[1])}}

需求是仅基于File属性对比两个集合，但输出结果中要同时包含Hash、File属性。

当前执行以下代码：

Compare-Object $file1 $file2 -Property File | Select Hash,File,SideIndicator

输出结果中Hash属性为空：

Hash File                                                   SideIndicator
---- ----                                                   -------------
     \steamapps\appmanifest_1036890.acf 798 20231122_123455 =>
     \steamapps\appmanifest_1091500.acf 687 20231122_125522 =>
     \steamapps\appmanifest_1036890.acf 798 20230919_003055 <=
     \steamapps\appmanifest_1091500.acf 925 20231026_112000 <=

原因分析 #

当使用Compare-Object仅指定File作为对比属性时，它只会生成包含File和SideIndicator的差异对象，原对象中的Hash属性不会被自动保留，因此直接选择Hash字段会显示为空。

解决方案 #

在对比出差异后，根据SideIndicator标记，从原集合$file1或$file2中匹配对应的File值，获取关联的Hash，再构建包含完整字段的对象输出：

$file1 = Get-Content -Path "hashlog1.log" | Select @{N='Hash'; E={($_ -split ' ',2)[0]}}, @{N='File'; E={(($_ -split ' ',2)[1])}}
$file2 = Get-Content -Path "hashlog2.log" | Select @{N='Hash'; E={($_ -split ' ',2)[0]}}, @{N='File'; E={(($_ -split ' ',2)[1])}}

# 对比差异并补充Hash字段
Compare-Object $file1 $file2 -Property File | ForEach-Object {
    # 根据来源标记获取对应的Hash值
    $targetHash = if ($_.SideIndicator -eq '<=') {
        ($file1 | Where-Object { $_.File -eq $_.File }).Hash
    } else {
        ($file2 | Where-Object { $_.File -eq $_.File }).Hash
    }

    # 输出包含完整字段的自定义对象
    [PSCustomObject]@{
        Hash = $targetHash
        File = $_.File
        SideIndicator = $_.SideIndicator
    }
}

输出结果 #

执行后会得到包含Hash的完整差异列表：

Hash                                 File                                                   SideIndicator
----                                 ----                                                   -------------
2E331B30A705D462541398874451A955    \steamapps\appmanifest_1036890.acf 798 20230919_003055 <=
88D100F2A7FFC2C912B59B45AED9DC48    \steamapps\appmanifest_1091500.acf 925 20231026_112000 <=
97CAF30C2E1F73ED121F75D947DB29C3    \steamapps\appmanifest_1036890.acf 798 20231122_123455 =>
78CF976F8BA64DAF19319E84B8133598    \steamapps\appmanifest_1091500.acf 687 20231122_125522 =>

内容的提问来源于stack exchange，提问作者HTWingNut