See
help about_Automatic_Variables
Automatic variables are maintained by the core and normally should not be used as parameters or local variables. This is easy to forget, especially with some simple variable names.
$Args
Contains an array of the undeclared parameters and/or parameter values that are passed to a function, script, or script block.
Test-1.Args.ps1 shows that $Args can be used as a parameter but it does not
work as one may expect.
$Input
Contains an enumerator that enumerates all input that is passed to a function.
Test-2.Input.ps1 shows that $Input can be used as a parameter but it does not
work as one may expect.
- Stack Overflow Args/params not being populated
- Stack Overflow Function parameter always empty why?
- Stack Overflow Why Pester does not mock a cmdlet with two parameters?
$$
Contains the last token in the last line received by the session.
$^
Contains the first token in the last line received by the session.
It is unlikely that $^ is used accidentally. But $$ is the easiest to type
variable, so it may be tempting to use it. In many cases these variables may be
used without problems but there are cases with issues.
Test-3.Dollar.ps1 and Test-4.Caret.ps1 show a case when $$ and $^ do
not work as normal variables in PowerShell v3+.
$This
In a script block that defines a script property or script method, the $This variable refers to the object that is being extended.
Test-5.This.ps1 shows an exotic case that may cause a crash or a strange error PowerShell v3. In PowerShell v2 it works with expected errors. See testing commands in the comments.
- Microsoft Connect 1423742