Powershell單雙引號字串的區別

最近做一些指令碼自動化的事情，發現一個很有意思的東西，如下，如果使用者賬戶包含了$符號，就會拋出一個“User cannot be found”的異常。

New-SPSite $CommunityUrl -OwnerAlias "ASIAPACIFIC`\$ExSquareDEV001" -Name "$CommunityName" -Template "STS#0" -ContentDatabase $CommunityDatabase
New-SPSite : User cannot be found.

上MSDN搜尋了一下，發現了一篇文章講述到了這個原因：http://technet.microsoft.com/en-us/library/ff730965.aspx

Quotation Marks in Windows PowerShell

First, let's review the basic distinction between single and double quotation marks in the Windows PowerShell language. It concerns the interpretation of variables.

• Double quotes. When a command or expression that includes variables is enclosed in double quotes ("), the variables are replaced by their values before the command is executed.

• Single quotes. When a command or expression that includes variables is enclosed in single quotes ('), the variables are not replaced by their values. Instead, they are interpreted literally.

There's actually a lot more to it – nested quotes and doubled quotes and escaped quotes and quotes in here-strings -- but these are the basics. For the rest, at the Windows PowerShell prompt, type:

• get-help about_quoting_rules

大意是由於$是PowerShell變數的標誌符號，所以不同的引號會做不同的處理。

雙引號內的PowerShell變數會先計算出值，然後輸出。

單引號內的PowerShell變數作為字串直接輸出。

看下面的一個樣本：

使用雙引號賦值，

變數賦值：$ExSquareServiceAccount = "ASIAPACIFIC\$ExSquareDEV001"

輸出變數值：ASIAPACIFIC\

由於後面的認成了變數，而並沒有賦值，這個時候就為空白，輸出就是前面的字串了。

如果使用單引號，

變數賦值：$ExSquareServiceAccount = 'ASIAPACIFIC\$ExSquareDEV001'

輸出變數值：ASIAPACIFIC\$ExSquareDEV001

整個字串不會進行變數替換，直接輸出。