PowerShell Question Mark Operator: Ternary, ??, ?. and $?

The question mark operator in PowerShell usually means the ternary operator, condition ? valueIfTrue : valueIfFalse. It picks one of two values in a single line, and it needs PowerShell 7 or later:

$diskFreeGB = 12

$status = $diskFreeGB -lt 20 ? 'Low disk space' : 'OK'
"Status: $status"

$servers = 'web01', 'web02', 'sql01'
"Found $($servers.Count) $($servers.Count -eq 1 ? 'server' : 'servers')"

Output:

Status: Low disk space
Found 3 servers

PowerShell also uses the question mark in ??, ??=, ?., as an alias and in $?. I cover each one below, with what works in Windows PowerShell 5.1.

The ternary operator in Windows PowerShell 5.1

Windows PowerShell 5.1 can’t even read a script that contains ? :. The parser rejects it before anything runs:

try { [void][scriptblock]::Create('$status = $diskFreeGB -lt 20 ? "Low" : "OK"'); 'Parsed fine' }
catch { 'Failed. Windows PowerShell 5.1 does not understand the ? : operator' }

Output:

Failed. Windows PowerShell 5.1 does not understand the ? : operator

Use an if statement as an expression instead. It works in every version and reads almost as well:

$diskFreeGB = 12

$status = if ($diskFreeGB -lt 20) { 'Low disk space' } else { 'OK' }
"Status: $status"

Output:

Status: Low disk space

If your script must run on older servers, stick with the if form. Comparison operators covers the conditions you can use.

?? and ??=: defaults for null values

The null-coalescing operator ?? returns the left side unless it’s $null, and the right side otherwise. ??= assigns a value only when the variable is $null:

$configuredPath = $null
$logPath = $configuredPath ?? 'C:\Logs\app.log'
"Log path: $logPath"

$region = $null
$region ??= 'us-east'
$region ??= 'us-west'
"Region: $region"

$emptyName = ''
"Empty string with ??: '$($emptyName ?? 'default')'"

Output:

Log path: C:\Logs\app.log
Region: us-east
Empty string with ??: ''

?? only reacts to $null. An empty string isn’t null, so it passes through unchanged. Check IsNullOrEmpty when empty text should get the default too.

?. and ?[]: safe property and index access

The null-conditional operators return $null instead of failing when the object is $null. Because ? is allowed in variable names, wrap the name in braces:

$user = $null
"Name with ?. : '$(${user}?.Name)'"

$user = [pscustomobject]@{ Name = 'Emma Carter'; Groups = @('Sales', 'VPN Users') }
"Name with ?. : '$(${user}?.Name)'"
"First group:   '$(${user}?.Groups?[0])'"

"Without braces: '$($user?.Name)'"

Output:

Name with ?. : ''
Name with ?. : 'Emma Carter'
First group:   'Sales'
Without braces: ''

Without the braces, PowerShell reads $user? as a separate variable that doesn’t exist, so you get nothing back. These operators need PowerShell 7.1 or later.

? as an alias for Where-Object

On its own, ? is a built-in alias for Where-Object, in every version. That’s the question mark you see in one-liners like this:

"Aliases for Where-Object: $((Get-Alias -Definition Where-Object).Name | Sort-Object)"

$big = 5, 18, 42, 7, 99 | ? { $_ -gt 10 }
"Values over 10: $($big -join ', ')"

Output:

Aliases for Where-Object: ? where
Values over 10: 18, 42, 99

Spell out Where-Object in scripts others will read. Where-Object covers filtering in depth.

$?: did the last command succeed?

The automatic variable $? is True when the last command succeeded and False when it reported an error:

Get-Item -Path C:\psfaqs\no-such-file.txt -ErrorAction SilentlyContinue
"After a failed command, `$? is $?"

Get-Date -Date '2026-09-29' | Out-Null
"After a successful command, `$? is $?"

Output:

After a failed command, $? is False
After a successful command, $? is True

Check it on the very next line, because every command resets it. Microsoft describes it in about_Automatic_Variables, and the other operators in about_Operators.

Frequently Asked Questions

Related operator guides:

• Comparison operators
• Arithmetic operators
• Check for null or empty strings
• Filter with Where-Object