Powershell，System.Diagnostics.Process和exiftool在处理数百个命令时停止工作

Question

我创建了一个工具(准确地说：Powershell脚本(来帮助我转换文件夹中的图片，即它查找某个结尾的所有文件(例如，*。TIF(，并通过ImageMagick将它们转换为JPEG。然后，它通过exiftool将一些EXIF，IPTC和XMP信息从源图像传输到JPEG：

# searching files (done before converting the files, so just listed for reproduction):
$WorkingFiles = @(Get-ChildItem -Path D:MyPicturesTestfiles -Filter *.tif | ForEach-Object {
[PSCustomObject]@{
SourceFullName = $_.FullName
JPEGFullName = $_.FullName -Replace 'tif$','jpg'
}
})
# Then, converting is done. PowerShell will wait until every jpeg is successfully created.
# + + + + The problem occurs somewhere after this line + + + +
# Creating the exiftool process:
$psi = New-Object System.Diagnostics.ProcessStartInfo
$psi.FileName = .exiftool.exe
$psi.Arguments = "-stay_open True -charset utf8 -@ -"
$psi.UseShellExecute = $false
$psi.RedirectStandardInput = $true
$psi.RedirectStandardOutput = $true
$psi.RedirectStandardError = $true
$exiftoolproc = [System.Diagnostics.Process]::Start($psi)
# creating the string argument for every file, then pass it over to exiftool:
for($i=0; $i -lt $WorkingFiles.length; $i++){
[string]$ArgList = "-All:all=`n-charset`nfilename=utf8`n-tagsFromFile`n$($WorkingFiles[$i].SourceFullName)`n-EXIF:All`n-charset`nfilename=utf8`n$($WorkingFiles[$i].JPEGFullName)"
# using -overwrite_original makes no difference
# Also, just as good as above code:
# [string]$ArgList = "-All:All=`n-EXIF:XResolution=300`n-EXIF:YResolution=300`n-charset`nfilename=utf8`n-overwrite_original`n$($WorkingFiles[$i].JPEGFullName)"
$exiftoolproc.StandardInput.WriteLine("$ArgList`n-execute`n")
# no difference using start-sleep:
# Start-Sleep -Milliseconds 25
}
# close exiftool:
$exiftoolproc.StandardInput.WriteLine("-stay_open`nFalse`n")
# read StandardError and StandardOutput of exiftool, then print it:
[array]$outputerror = @($exiftoolproc.StandardError.ReadToEnd().Split("`r`n",[System.StringSplitOptions]::RemoveEmptyEntries))
[string]$outputout = $exiftoolproc.StandardOutput.ReadToEnd()
$outputout = $outputout -replace '======== ','' -replace '[1/1]','' -replace ' rn    '," - " -replace '{ready}rn',''
[array]$outputout = @($outputout.Split("`r`n",[System.StringSplitOptions]::RemoveEmptyEntries))
Write-Output "Errors:"
foreach($i in $outputerror){
Write-Output $i
}
Write-Output "Standard output:"
foreach($i in $outputout){
Write-Output $i
}

---

如果你想复制但没有/想要那么多文件，还有一个更简单的方法：让exiftool打印出它的版本号600次：

$psi = New-Object System.Diagnostics.ProcessStartInfo
$psi.FileName = .exiftool.exe
$psi.Arguments = "-stay_open True -charset utf8 -@ -"
$psi.UseShellExecute = $false
$psi.RedirectStandardInput = $true
$psi.RedirectStandardOutput = $true
$psi.RedirectStandardError = $true
$exiftoolproc = [System.Diagnostics.Process]::Start($psi)
for($i=0; $i -lt 600; $i++){
try{
$exiftoolproc.StandardInput.WriteLine("-ver`n-execute`n")
Write-Output "Success:`t$i"
}catch{
Write-Output "Failed:`t$i"
}
}
# close exiftool:
try{
$exiftoolproc.StandardInput.WriteLine("-stay_open`nFalse`n")
}catch{
Write-Output "Could not close exiftool!"
}
[array]$outputerror = @($exiftoolproc.StandardError.ReadToEnd().Split("`r`n",[System.StringSplitOptions]::RemoveEmptyEntries))
[array]$outputout = @($exiftoolproc.StandardOutput.ReadToEnd().Split("`r`n",[System.StringSplitOptions]::RemoveEmptyEntries))
Write-Output "Errors:"
foreach($i in $outputerror){
Write-Output $i
}
Write-Output "Standard output:"
foreach($i in $outputout){
Write-Output $i
}

---

据我测试，一切顺利，只要你<115 个文件。如果你上面，第 114^个JPEG 会获得正确的元数据，但 exiftool 在此之后停止工作 - 它会空闲，我的脚本也会这样做。我可以使用不同的文件、路径和 exiftool 命令重现这一点。

即使有exiftool的-verbose旗帜，StandardOutput和StandardError也没有表现出任何违规行为 - 当然，他们不会，因为我必须杀死exiftool才能让他们出现。

运行ISE/VSCode的调试器不显示任何内容。Exiftool的窗口(仅在调试时显示(不显示任何内容。

使用System.Diagnostics.Process运行的命令是否有一些硬限制，这是 exiftool 的问题，还是仅仅是因为我无法使用最基本的 Powershell cmdlet 之外的东西？或者也许更好的问题是：我如何正确调试它？

---

Powershell是5.1，exiftool是10.80(生产(- 10.94(最新(。

Answer 1

在弄乱了$ArgList的不同变体后，我发现使用不同的文件命令时没有区别，但是使用产生较少 StdOut(如-ver(的命令会导致更多的迭代。因此，我做了一个有根据的猜测，即输出缓冲区是罪魁祸首。

根据马克·拜尔斯(Mark Byers(对"ProcessStartInfo挂在"WaitForExit"上的回答？为什么？

问题是，如果重定向标准输出和/或标准错误，内部缓冲区可能会变满。[...]

解决方案是使用异步读取来确保缓冲区不会变满。

然后，这只是寻找正确事物的问题。我发现Alexander Obersht对"如何在powershell中异步捕获进程输出？"的回答几乎提供了我需要的一切。

脚本现在如下所示：

# searching files (done before converting the files, so just listed for reproduction):
$WorkingFiles = @(Get-ChildItem -Path D:MyPicturesTestfiles -Filter *.tif | ForEach-Object {
[PSCustomObject]@{
SourceFullName = $_.FullName
JPEGFullName = $_.FullName -Replace 'tif$','jpg'
}
})
# Then, converting is done. PowerShell will wait until every jpeg is successfully created.
# Creating the exiftool process:
$psi = New-Object System.Diagnostics.ProcessStartInfo
$psi.FileName = .exiftool.exe
$psi.Arguments = "-stay_open True -charset utf8 -@ -"
$psi.UseShellExecute = $false
$psi.RedirectStandardInput = $true
$psi.RedirectStandardOutput = $true
$psi.RedirectStandardError = $true
# + + + + NEW STUFF (1/2) HERE: + + + +
# Creating process object.
$exiftoolproc = New-Object -TypeName System.Diagnostics.Process
$exiftoolproc.StartInfo = $psi
# Creating string builders to store stdout and stderr.
$exiftoolStdOutBuilder = New-Object -TypeName System.Text.StringBuilder
$exiftoolStdErrBuilder = New-Object -TypeName System.Text.StringBuilder
# Adding event handers for stdout and stderr.
$exiftoolScripBlock = {
if (-not [String]::IsNullOrEmpty($EventArgs.Data)){
$Event.MessageData.AppendLine($EventArgs.Data)
}
}
$exiftoolStdOutEvent = Register-ObjectEvent -InputObject $exiftoolproc -Action $exiftoolScripBlock -EventName 'OutputDataReceived' -MessageData $exiftoolStdOutBuilder
$exiftoolStdErrEvent = Register-ObjectEvent -InputObject $exiftoolproc -Action $exiftoolScripBlock -EventName 'ErrorDataReceived' -MessageData $exiftoolStdErrBuilder
[Void]$exiftoolproc.Start()
$exiftoolproc.BeginOutputReadLine()
$exiftoolproc.BeginErrorReadLine()
# + + + + END OF NEW STUFF (1/2) + + + +
# creating the string argument for every file, then pass it over to exiftool:
for($i=0; $i -lt $WorkingFiles.length; $i++){
[string]$ArgList = "-All:all=`n-charset`nfilename=utf8`n-tagsFromFile`n$($WorkingFiles[$i].SourceFullName)`n-EXIF:All`n-charset`nfilename=utf8`n$($WorkingFiles[$i].JPEGFullName)"
# using -overwrite_original makes no difference
# Also, just as good as above code:
# [string]$ArgList = "-All:All=`n-EXIF:XResolution=300`n-EXIF:YResolution=300`n-charset`nfilename=utf8`n-overwrite_original`n$($WorkingFiles[$i].JPEGFullName)"
$exiftoolproc.StandardInput.WriteLine("$ArgList`n-execute`n")
}
# + + + + NEW STUFF (2/2) HERE: + + + +
# close exiftool:
$exiftoolproc.StandardInput.WriteLine("-stay_open`nFalse`n")
$exiftoolproc.WaitForExit()
# Unregistering events to retrieve process output.
Unregister-Event -SourceIdentifier $exiftoolStdOutEvent.Name
Unregister-Event -SourceIdentifier $exiftoolStdErrEvent.Name
# read StandardError and StandardOutput of exiftool, then print it:
[array]$outputerror = @($exiftoolStdErrBuilder.ToString().Trim().Split("`r`n",[System.StringSplitOptions]::RemoveEmptyEntries))
[string]$outputout = $exiftoolStdOutBuilder.ToString().Trim() -replace '======== ','' -replace '[1/1]','' -replace ' rn    '," - " -replace '{ready}rn',''
[array]$outputout = @($outputout.Split("`r`n",[System.StringSplitOptions]::RemoveEmptyEntries))
# + + + + END OF NEW STUFF (2/2) + + + +
Write-Output "Errors:"
foreach($i in $outputerror){
Write-Output $i
}
Write-Output "Standard output:"
foreach($i in $outputout){
Write-Output $i
}

我可以确认它适用于很多很多文件(至少 1600 个(。