PowerTip of the Day from powershell.com上周汇总（十一）

删除错误记录

Deleting Error Records

http://powershell.com/cs/blogs/tips/archive/2010/10/11/deleting-eating-error-records.aspx

Trap { "Whew, an error: $_"; continue } 1/$null

如果不加continue，红色的错误信息会显示出来。

 

 

改变ErrorAction

Change ErrorAction for Your Private Error Handling

http://powershell.com/cs/blogs/tips/archive/2010/10/12/change-erroraction-for-your-private-error-handling.aspx

比如：

$local:ErrorActionPreference = "Stop"

$local:ErrorActionPreference = "SilentlyContinue"

 

 

使用Break

Do You Use "Break"?

http://powershell.com/cs/blogs/tips/archive/2010/10/13/do-you-use-quot-break-quot.aspx

作用，直接终止循环。

Do {
$pwd = Read-Host 'Enter your password'
If ($pwd -eq 'topsecret') { break }
} While ($true)

 

 

 

理解变量继承（作用域）

Understanding Variable Inheritance

http://powershell.com/cs/blogs/tips/archive/2010/10/14/understanding-variable-inheritance.aspx

$a = 1
Function test {
    "variable a contains $a"
    $a = 2
    "variable a contains $a"
}
test
variable a contains 1
variable a contains 2
然后输入

$a

输出的结果是
1

变量可以从父级继承过来，但是如果在自己的作用域再声明的话，那么它们就不是一个变量了。

 

 

创建静态变量

Creating "Static" Variables

http://powershell.com/cs/blogs/tips/archive/2010/10/15/creating-quot-static-quot-variables.aspx

Function test {
$script:nestlevel += 1
If ($script:nestlevel -gt 10) { break }
"I am at nest level $script:nestlevel"
Test
}
test

代码用到了递归。每次迭代访问静态变量。

 

 

使用私有变量

Working with Private Variables

http://powershell.com/cs/blogs/tips/archive/2010/10/18/working-with-private-variables.aspx

变量可以向下继承，即子方法可以调用父级代码的变量。如果想要避免这种调用关系的话，需要用到私有变量。

$private:a = 1
Function test {
    "variable a contains $a"
    $a = 2
    "variable a contains $a"
}
test
variable a contains
variable a contains 2
$a
1

可以看出父级私有变量a在方法里并没有被访问到。

 

 

改变控制台颜色

Changing Console Colors

http://powershell.com/cs/blogs/tips/archive/2010/10/19/changing-console-colors.aspx

$host.UI.RawUI.BackgroundColor = 'Blue'
[System.Console]::BackgroundColor = 'Blue'

 

 

重置控制台颜色

Resetting Console Colors

http://powershell.com/cs/blogs/tips/archive/2010/10/20/resetting-console-colors.aspx

改变颜色：

[System.Console]::BackgroundColor = 'Blue'
[System.Console]::ForegroundColor = 'Yellow'
Clear-Host

恢复颜色：

[System.Console]::ResetColor()
Clear-Host

 

 

清空控制台内容

Clearing Console Content

http://powershell.com/cs/blogs/tips/archive/2010/10/21/clearing-console-content.aspx

可以用cls和Clear-Host。但是这两种方法性能不高。

get-command clear-host | Select-Object -expand Definition
$space = New-Object System.Management.Automation.Host.BufferCell
$space.Character = ' '
$space.ForegroundColor = $host.ui.rawui.ForegroundColor
$space.BackgroundColor = $host.ui.rawui.BackgroundColor
$rect = New-Object System.Management.Automation.Host.Rectangle
$rect.Top = $rect.Bottom = $rect.Right = $rect.Left = -1
$origin = New-Object System.Management.Automation.Host.Coordinates
$Host.UI.RawUI.CursorPosition = $origin
$Host.UI.RawUI.SetBufferContents($rect, $space)

重写Clear-Host函数，性能就提高多了：

Function Clear-Host { [System.Console]::Clear() }

 

 

显示可以字符集(?)

Listing Available Culture IDs

http://powershell.com/cs/blogs/tips/archive/2010/10/22/listing-available-culture-ids.aspx

[System.Globalization.CultureInfo]::GetCultures('WindowsOnlyCultures')

也可以指定控制台使用何种字符集。

$c = [System.Globalization.CultureInfo]'ar-IQ'
[System.Threading.Thread]::CurrentThread.CurrentCulture = $c; Get-Date

 

 

把字符集转换成国家名

Translating Culture IDs to Country Names

http://powershell.com/cs/blogs/tips/archive/2010/10/25/translating-culture-ids-to-country-names.aspx

[System.Globalization.CultureInfo]::GetCultureInfoByIetfLanguageTag('ar-IQ')

显示结果：

LCID Name DisplayName

---- ---- -----------

2049 ar-IQ Arabic (Iraq)

 

 

执行程序并且保持联系（即对它的控制）

Launching Programs and Keeping in Touch

http://powershell.com/cs/blogs/tips/archive/2010/10/26/launching-programs-and-keeping-in-touch.aspx

Start-Process加上-passThru参数就可以让其返回一个Process对象的引用，这样后面就可以控制这个进程。

$process = Start-Process notepad.exe -passThru
$process
$process.Kill()

 

 

以提升模式（？）运行程序

Run Programs Elevated

http://powershell.com/cs/blogs/tips/archive/2010/10/27/run-programs-elevated.aspx

当UAC开启时，想要以提升模式运行程序。

Start-Process powershell -verb runas

 

 

使用不同的用户运行程序

Running Programs as Different User

http://powershell.com/cs/blogs/tips/archive/2010/10/28/running-programs-as-different-user.aspx

Start-Process powershell -LoadUserProfile -Credential (Get-Credential)

会弹出界面提示以哪个用户运行。

 

 

根据关键字查找方法

Finding Methods with Specific Keywords

http://powershell.com/cs/blogs/tips/archive/2010/10/29/finding-methods-with-specific-keywords.aspx

$key = 'Kill'[System.Diagnostics.Process].Assembly.GetExportedTypes() | Where-Object { $_.isPublic}| Where-Object { $_.isClass } | Where-Object { @($_.GetMethods() | Where-Object { $_.Name -like "*$key*" }).Count -gt 0 } | Select-Object -expandProperty FullName

感觉不如直接查MSDN的方便。