powershell - 使用start子命令为循环改进批处理文件

Question

我目前有一个非常简单的脚本，可以ping 10个IP:

@ECHO OFF
for /L %%i in (100, 1, 110) DO (
  START /W /B cmd /c ping -n 1 192.168.0.%%i | find "time="
)

输出是预期的:

C:\Users\herpderp>test.batReply from 192.168.0.101: bytes=32 time=294ms TTL=64Reply from 192.168.0.104: bytes=32 time=1ms TTL=64

However, it is VERY slow and definitely happening sequentially. When I run this with a PowerShell Measure-Command I get these results:

PS C:\Users\derpherp> measure-command {start-process test.bat -Wait}Days              : 0Hours             : 0Minutes           : 0Seconds           : 23Milliseconds      : 107Ticks             : 231074173TotalDays         : 0.000267446959490741TotalHours        : 0.00641872702777778TotalMinutes      : 0.385123621666667TotalSeconds      : 23.1074173TotalMilliseconds : 23107.4173

So we see it is taking ~23 seconds to execute.

Now, if I were on a Linux system and wanted to do this same thing, I can do the following:

#!/bin/bash

for ip in $(seq 100 110); do
  ping -c 1 192.168.0.$ip | grep "bytes from" | cut -d" " -f4 | cut -d ":" -f1 &
done

结果在多种方面有所不同:

结果并不总是顺序的，这意味着它实际上以更异步的方式启动了命令:

root@kali:~/vids/bash_scripting# ./test.sh192.168.0.104192.168.0.100192.168.0.103192.168.0.101

The time for it to display all of the positive results is typically less than a second and this scales to much larger sets of numbers.

So, my question, is this a limitation of batch scripting? I find it hard to believe that bash performs literally 100s of times better than Windows CMD interpreter for such a simple task?

If this is limited, does PowerShell offer a competitive way to create tasks? I've used Start-Job in a foreach loop but that seems to become unworkable for large numbers of tasks (ie Test-Connection on a /16 network)

Edit 1

@ECHO OFF
for /L %%i in (100, 1, 110) DO (
  ping -n 1 192.168.0.%%i | find "time="
)

这将输出当前窗口并花费与初始变体一样长的时间

@ECHO OFF
for /L %%i in (100, 1, 110) DO (
  START ping -n 1 192.168.0.%%i | find "time="
)

这将输出到每个IP的唯一窗口，并且只需花费很长时间即可完成。

Answer 1

异步并不是一件容易的事，但是使用PowerShell，您可以很轻松地完成工作。

此代码的行为应类似于您的bash代码，返回所有无错误响应的主机的IP地址:

$IPAddresses = 100..110 | ForEach-Object { "192.168.0.$_"; }

$JobList = $IPAddresses | ForEach-Object {
    Test-Connection -ComputerName $_ -Count 1 -AsJob;
}

Receive-Job -Job $JobList -AutoRemoveJob -Wait | `
    Where-Object { $_.StatusCode -eq 0 } | `
    Select-Object -ExpandProperty Address;

在3秒内，针对约250个主机，以上对我而言已完成。
Test-Connection本身声称最多使用32个同时连接(可通过 -ThrottleLimit设置配置)，但是如果您要定位的目标范围很广，则 -Delay选项似乎可以完全覆盖该设置。

您可能会遇到PowerShell v4及更早版本的问题，因为它的行为可能略有不同。特别是 Test-Connection在Windows或PowerShell的不同版本上似乎是特质的。至少，我一直记得它在以前的版本中抛出错误而不是返回错误状态代码。

如果您想对ping进行更精细的控制，而不是 Test-Connection给您提供-例如，它默认为1秒超时，因此当任何主机关闭时您要等待的最短时间为1秒-您可能必须恢复为直接调用 Get-WMIObject -Query "SELECT * FROM Win32_PingStatus WHERE Address = '$IP' AND TimeOut = 200" -AsJob。