How to Invoke Expressions Using PowerShell

1. the Invoke-Expression in PowerShell
2. Pass Parameters to Scripts With Invoke-Expression in PowerShell
3. Difference of Invoke-Expression From the Call Operator in PowerShell
4. Difference of Invoke-Command From Invoke-Expression in PowerShell

The Invoke-Expression PowerShell cmdlet can easily be misunderstood when and when not to use it.

This article will teach us how Invoke-Expression works and how we can put it into practical use.

the Invoke-Expression in PowerShell

The Invoke-Expression command evaluates or runs a specific string as a form of script block and returns the results of the command or expression. It can help call the code within a script, build commands to be executed later, or use it cautiously with user-provided input.

One example of Invoke-Expression is defining a script and passing that string to the Command parameter.

Script Sample:

$getProcess = 'Get-Process'
Invoke-Expression -Command $getProcess

$pathFile = '.\Test.ps1'
Invoke-Expression -Command $pathFile

Invoke-Expression will execute the script as expected if you enclose the path item in double "" or single quotes'' with the entire string in quotes. You can also indicate the full path location of the script file like the sample below.

Script Sample:

$pathFile = "C:\'Folder Path'\Test.ps1"
Invoke-Expression $pathFile

Pass Parameters to Scripts With Invoke-Expression in PowerShell

There is no native method to pass parameters with Invoke-Expression, but we can include them in the string you give to the Command parameter. Instead of using a parameter via Invoke-Expression, we can pass parameters to that script by giving them.

We have to include that entire line in a string and then pass that string to the Command parameter.

Script Sample:

$pathFile = 'C:\Scripts\Test.ps1'
$scriptParam = '-Path "C:\file.txt" -Force'
Invoke-Expression "$pathFile $scriptParam"

# or

$pathFile = 'C:\Scripts\Test.ps1 -Path "C:\test_file.txt" -Force'
Invoke-Expression $pathFile

Difference of Invoke-Expression From the Call Operator in PowerShell

The call operator (&) is used to execute a script, script block, or command, but it does not interpret command parameters as Invoke-Expression does.

For example, we will get the PowerShell Core process using the Get-Process -ProcessName pwsh cmdlet. Unfortunately, using the call operator, concatenating Get-Process and the parameter will not work.

Script Sample:

$getProc = "Get-Process"

## The script below will not work
& "$getProc pwsh"

The command will execute if we run this string with Invoke-Expression as shown below.

Script Sample:

Invoke-Expression "$getProc pwsh"

Difference of Invoke-Command From Invoke-Expression in PowerShell

Only a string is converted to executable code by the Invoke-Expression cmdlet. In contrast, the Invoke-Command command allows us to run programs on computers remotely or locally.

The Invoke-Command cmdlet is preferable if we are writing the executed commands now, as we retain IntelliSense in our IDE, whereas Invoke-Expression would be preferable if we wanted to call another script from within our current one.

Script Sample:

## Invoke-Command
Invoke-Command -ScriptBlock {
    Get-Process PowerShell
}

## Invoke-Expression
Invoke-Expression -Command "
    Get-Process PowerShell
"