[PowerShell每日技巧]字符串中的变量扩展(20140226)

DAIC

To insert a variable into a string, you probably know that you can use double quotes like this:

1. $domain = $env:USERDOMAIN
   
2. $username = $env:USERNAME
   
3. 
   
4. "$domain\$username"

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This works well as long as it is clear to PowerShell where your variables start and end. Check this out:

1. $domain = $env:USERDOMAIN
   
2. $username = $env:USERNAME
   
3. 
   
4. "$username: located in domain $domain"

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This fails, because PowerShell adds the colon to the variable (as indicated by the token colors).

You can use the PowerShell backtick escape character to escape special characters like the colon:

1. $domain = $env:USERDOMAIN
   
2. $username = $env:USERNAME

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1. "$username`: located in domain $domain"

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This will not help you, though, if the problem was not caused by a special character in the first place:

1. "Current Background Color: $host.UI.RawUI.BackgroundColor"

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Token colors indicate that double quoted strings only resolve the variable and nothing else (nothing that follows the variable name, like accessing object properties).

To solve this problem, you must use one of these techniques:

1. "Current Background Color: $($host.UI.RawUI.BackgroundColor)"

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1. 'Current Background Color: ' + $host.UI.RawUI.BackgroundColor

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1. 'Current Background Color: {0}' -f $host.UI.RawUI.BackgroundColor

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http://powershell.com/cs/blogs/tips/archive/2014/02/26/expanding-variables-in-strings.aspx

DAIC

除了用反引号对冒号进行转义，还可以用 ${}

1. $domain = $env:USERDOMAIN
   
2. $username = $env:USERNAME
   
3. "${username}: located in domain ${domain}"

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