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I'm using PowerShell scripts for some UI automation of a WPF application. Normally, the scripts are run as a group, based on the value of a global variable. It's a little inconvenient to set this variable manually for the times when I want to run just one script, so I'm looking for a way to modify them to check for this variable and set it if not found.
test-path variable:\foo doesn't seem to work, since I still get the following error:
The variable '$global:foo' cannot be retrieved because it has not been set.
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Environment] to retrieve the specific or all environment variables. To retrieve all environment variables use GetEnvironmentVariables() class. To get the specific environment variable using . Net method use GetEnvironmentVariable() method.
To declare a PowerShell global variable, simply use the below syntax. $global: myVariable ="This is my first global variable." If you choose not to give any value to it, you can explicitly assign a null value to it.
PowerShell scope protects variables and other artifacts by limiting where they can be read and modified. Scope levels protect items that should not be changed. PowerShell has the following scopes available: Global: This scope is available when you open a PowerShell console or create a new runspace or session.
The echo command is used to print the variables or strings on the console. The echo command has an alias named “Write-Output” in Windows PowerShell Scripting language. In PowerShell, you can use “echo” and “Write-Output,” which will provide the same output.
Test-Path can be used with a special syntax:
Test-Path variable:global:foo This also works for environment variables ($env:foo):
Test-Path env:foo And for non-global variables (just $foo inline):
Test-Path variable:foo EDIT: Use stej's answer below. My own (partially incorrect) one is still reproduced here for reference:
You can use
Get-Variable foo -Scope Global and trap the error that is raised when the variable doesn't exist.
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