What does $$, $?, $^ represent in powershell?

Saw these variables in the debugger and I'm n开发者_Go百科ot sure what they do.

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• $_ The current pipeline object; used in script blocks, filters, the process clause of functions, where-object, foreach-object and switch
• $^ contains the first token of the last line input into the shell
• $$ contains the last token of last line input into the shell
• $? Contains the success/fail status of the last statement

Source: http://www.computerperformance.co.uk/powershell/powershell_variables.htm#%24Dollar_variables_

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Read

Get-Help About_Automatic_Variables

Its all about the goodness of automatic variables that get created when using PowerShell console.

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In PowerShell, a dollar sign preceding a name indicates a variable. The symbols in question are just special cases of variables provided by the PowerShell environment. They are also known as "automatic" variables. More specifically:

• $$ is a variable containing the last token of the last line input into the shell
  (does not contain the whole command)

• $^ is a variable containing the first token of the last line input into the shell
  (does not contain the whole command)

• $? is a variable containing the success or failure of the last statement
  (False if the previous command ended with an error; True otherwise.)