PowerShell对比文本文件差异并邮件发送的代码异常排查

我有两个存储SQL函数名称列表的文本文件，想要对比$A与$B的内容，筛选出仅存在于$B而不存在于$A的SQL函数名称并写入$C文件，再将$C作为附件发送至指定邮箱。

我的代码如下：

$A = "c:\ReferenceFunctions.txt" 
$B = "c:\GeneratedFunctions.txt" 
$C = "c:\FileWithDifferences.txt" 
$fromaddress = "noreply@xyz" 
$toaddress = "123@hhh" 
$bccaddress = "3333@nnn.com" 
$login = "yourlogin" 
$password = "password" | Convertto-SecureString -AsPlainText -Force 
$smtpserver = "gggg.com" 
$smtp = new-object Net.Mail.SmtpClient($smtpserver, 800) 
$smtp.EnableSsl = $true 
$smtp.Credentials = New-Object System.Net.NetworkCredential($login, $password); 
$body = "see attached " 
$Subject = "checking differences" 
$message = new-object System.Net.Mail.MailMessage 
$message.From = $fromaddress 
$message.To.Add($toaddress) 
#$message.CC.Add($CCaddress) 
$message.Bcc.Add($bccaddress) 
$message.IsBodyHtml = $True 
$message.Subject = $Subject 
$message.body = $body 
$message.Priority = [System.Net.Mail.MailPriority]::High 

Compare-object (Get-Content $A) (Get-Content $B) | Out-File $C 

#Attach the eported file with differences 
$attachment = $C 
$attach = new-object Net.Mail.Attachment($attachment) 
$message.Attachments.Add($attach) 

IF (Compare-Object -ReferenceObject (Get-Content $A) -DifferenceObject (Get-Content $B)){ 
    $smtp.Send($message); 
}

$A文件内容：

fn_StatementEndOfMonth fn_Performance_Sql fn_DailyReturns

$B文件内容：

fn_Performance_Sql fn_DailyReturns fn_SQLPerfomance_Monitor

预期$C文件应包含：

fn_SQLPerfomance_Monitor

但当前代码执行后，附件中包含了两个文件中的所有SQL函数名称，而非预期的差异内容，我无法定位问题所在，请求协助排查。

我帮你梳理了代码里的问题，核心有两个关键点：

问题根源 #

1. 文件内容读取方式错误：你的函数名是在同一行用空格分隔的，Get-Content默认会把整行内容当成一个字符串项，而不是拆分单个函数名。这会导致Compare-Object对比的是两行完整内容，自然会认为两边都是差异项，输出所有内容。
2. Compare-Object默认行为不符合需求：默认情况下，它会返回两边所有差异项（包括仅在$A的<=标记项和仅在$B的=>标记项），且输出包含额外格式，直接写入文件会出现不符合预期的内容。

分步修复 #

1. 拆分文件中的函数名 #

先把单行空格分隔的内容拆分成单个函数名数组，确保对比逻辑针对每个函数：

$contentA = (Get-Content $A) -split '\s+' | Where-Object { $_ -ne '' }
$contentB = (Get-Content $B) -split '\s+' | Where-Object { $_ -ne '' }

用-split '\s+'按任意空白字符拆分，再过滤空字符串避免无效项。

2. 筛选仅存在于$B的函数 #

对比拆分后的数组，筛选出SideIndicator为=>的项（仅属于$B的函数），提取纯函数名：

$onlyInB = Compare-Object -ReferenceObject $contentA -DifferenceObject $contentB | 
           Where-Object { $_.SideIndicator -eq '=>' } | 
           Select-Object -ExpandProperty InputObject

3. 写入结果文件 #

把筛选后的结果写入$C，确保每行一个函数名：

$onlyInB | Out-File $C -Encoding utf8

4. 优化邮件发送逻辑 #

检查是否有差异内容，避免发送空附件的邮件，同时清理资源防止内存泄漏：

if ($onlyInB) {
    $attach = New-Object Net.Mail.Attachment($C)
    $message.Attachments.Add($attach)
    $smtp.Send($message)
    $attach.Dispose()
}
$smtp.Dispose()

修复后的完整代码 #

$A = "c:\ReferenceFunctions.txt" 
$B = "c:\GeneratedFunctions.txt" 
$C = "c:\FileWithDifferences.txt" 
$fromaddress = "noreply@xyz" 
$toaddress = "123@hhh" 
$bccaddress = "3333@nnn.com" 
$login = "yourlogin" 
$password = "password" | Convertto-SecureString -AsPlainText -Force 
$smtpserver = "gggg.com" 
$smtp = New-Object Net.Mail.SmtpClient($smtpserver, 800) 
$smtp.EnableSsl = $true 
$smtp.Credentials = New-Object System.Net.NetworkCredential($login, $password); 
$body = "see attached " 
$Subject = "checking differences" 
$message = New-Object System.Net.Mail.MailMessage 
$message.From = $fromaddress 
$message.To.Add($toaddress) 
#$message.CC.Add($CCaddress) 
$message.Bcc.Add($bccaddress) 
$message.IsBodyHtml = $True 
$message.Subject = $Subject 
$message.body = $body 
$message.Priority = [System.Net.Mail.MailPriority]::High 

# 修复：拆分函数名并筛选仅在B中的项
$contentA = (Get-Content $A) -split '\s+' | Where-Object { $_ -ne '' }
$contentB = (Get-Content $B) -split '\s+' | Where-Object { $_ -ne '' }
$onlyInB = Compare-Object -ReferenceObject $contentA -DifferenceObject $contentB | 
           Where-Object { $_.SideIndicator -eq '=>' } | 
           Select-Object -ExpandProperty InputObject

# 写入结果文件
$onlyInB | Out-File $C -Encoding utf8

# 仅当有差异时发送邮件
if ($onlyInB) {
    $attach = New-Object Net.Mail.Attachment($C)
    $message.Attachments.Add($attach)
    $smtp.Send($message)
    $attach.Dispose()
}

# 清理SMTP客户端资源
$smtp.Dispose()

这样修改后，$C文件就会只包含fn_SQLPerfomance_Monitor，完全符合你的预期啦。

内容的提问来源于stack exchange，提问作者Immortal