Question

I am confused with ForEach-Object -Parallel. The following code has $blobs array with more than 2000 blobs. With the regular foreach I can print the names of each blob without a problem. Then using the ForEach-Object -Parallel just after the first foreach, nothing is printed. Why ?

foreach ($blob in $blobs) {
           Write-Host    $blob.Name
}

# Use parallel processing to process blobs concurrently
$blobs|ForEach-Object -Parallel {
         param (
             $blob)
    
        Write-Host $blob.Name 
} -ThrottleLimit 300

Answer 1

The script block passed to a ForEach-Object cmdlet call - whether or not you use -Parallel - receives its (pipeline) input implicitly, via the automatic $_ variable (aka $PSItem):

$blobs |
  ForEach-Object -Parallel {
    $_.Name
  }

相比之下,foreach >>>>>>>>> /em> 要求自选/m>>(例如$/)。
Perhaps confusingly, foreach is also an alias of the ForEach-Object cmdlet, and it is the syntactic context that decides whether foreach refers to the language statement or the cmdlet.

请注意,<代码>-ThrottleLimit 参数控制了允许多少座标/>在时间<>上<>。对万国邮联业务而言,规定数量比现存的万国邮联核心数要高,只是针对网络约束、I/O约束或等待事件,才有意义。

<>ForEach-Objectcmdlet,$_在-Parallel上同时使用或未使用-Parallel,从打电话的人的称谓范围来看,在查询variables上存在重大差别:

With -Parallel, you need the $using: scope; e.g.:

$foo = bar # Note the $using:foo reference. # *Without* -Parallel, use just $foo # -> bar1 , bar2 , bar3 1..3 | ForEach-Object -Parallel { $using:foo + $_ }

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