PowerShell:在函数内处理调用结果 - 最佳实践 [英] PowerShell: Disposing of a call result within a function - best practice

问题描述

我有一个函数，在该函数中，我调用了一个 git 函数:

I have a function, and within that function, I am calling a git function:

function Confirm-GitStatus
{
    # a bunch of stuff
    & git --git-dir $gitDir --work-tree $basePath  checkout $targetBranch 2>&1
    # more stuff
    return $true
}

这个结果实际上是一个包含 git 调用结果和 $true 的数组.为了得到我想要的结果，我不得不这样做:

The result of this is actually an array containing the result of the the git call and $true. In order to get the result I wanted, I had to do this:

$disposableMessage = & git --git-dir $gitDir --work-tree $basePath  checkout $targetBranch 2>&1

这感觉很恶心.拨打电话并抛出结果的最佳做法是什么?

This feels gross. What is the best practice for making calls and tossing the result?

推荐答案

由于您无论如何都在使用流重定向 - 2>&1 来合并 PowerShell错误流(从git 的stderr)到成功流(从stdout))——最简单的解决方案是重定向所有流(*) 到 $null 和 *>$null;一个简化的例子:

Since you're using a stream redirection anyway - 2>&1 to merge the PowerShell error stream (from git's stderr) to the success stream (from stdout)) - the simplest solution is to redirect all streams (*) to $null with *> $null; a simplified example:

# Note: This command produces both stdout and stderr output.
cmd /c "echo hi & dir \nosuch" *> $null

# PowerShell Core example with Bash:
bash -c 'echo hi; ls \nosuch'  *> $null

---

但是，通常考虑$null = ...丢弃命令的(成功)输出，因为它:

---

However, in general consider $null = ... for discarding a command's (success) output, because it:

• 传达意图预先

比 > 都快$null 尤其是 ... |大多数情况下为 Out-Null.^[1]

应用于以上示例:

$null = cmd /c "echo hi & dir \nosuch" 2>&1

$null = bash -c 'echo hi; ls \nosuch'  2>&1

---

^{[1] 在 PowerShell (Core) 6+ 中，Out-Null 有一个优化，如果前面的管道段是一个无副作用的表达式而不是方法或命令调用；例如，1..1e6 |Out-Null 几乎立即执行，因为该表达式似乎甚至没有执行.然而，这种情况是非典型的，功能上等效的 Write-Output (1..1e6) |Out-Null 需要很长时间才能运行，远比 $null = Write-Output (1..1e6) 长.}

---

^{[1] In PowerShell (Core) 6+, Out-Null has an optimization if the only preceding pipeline segment is a side effect-free expression rather than a method or command call; e.g., 1..1e6 | Out-Null executes in almost no time, because the expression is seemingly not even executed. However, such a scenario is atypical, and the functionally equivalent Write-Output (1..1e6) | Out-Null takes a long time to run, much longer than $null = Write-Output (1..1e6).}

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