From what I know, PowerShell doesn't seem to have a built-in expression for the so-called ternary operator.
For example, in the C language, which supports the ternary operator, I could write something like:
<condition> ? <condition-is-true> : <condition-is-false>;If that doesn't really exist in PowerShell, what would be the best way (i.e. easy to read and to maintain) to accomplish the same result?
714 Answers
$result = If ($condition) {"true"} Else {"false"}For use in or as an expression, not just an assignment, wrap it in $(), thus:
write-host $(If ($condition) {"true"} Else {"false"}) Powershell 7 has it.
PS C:\Users\js> 0 ? 'yes' : 'no'
no
PS C:\Users\js> 1 ? 'yes' : 'no'
yesThe closest PowerShell construct I've been able to come up with to emulate that is:
@({'condition is false'},{'condition is true'})[$condition]Per this PowerShell blog post, you can create an alias to define a ?: operator:
set-alias ?: Invoke-Ternary -Option AllScope -Description "PSCX filter alias"
filter Invoke-Ternary ([scriptblock]$decider, [scriptblock]$ifTrue, [scriptblock]$ifFalse)
{ if (&$decider) { &$ifTrue } else { &$ifFalse }
}Use it like this:
$total = ($quantity * $price ) * (?: {$quantity -le 10} {.9} {.75})Try powershell's switch statement as an alternative, especially for variable assignment - multiple lines, but readable.
Example,
$WinVer = switch ( Test-Path "$Env:windir\SysWOW64" ) { $true { "64-bit" } $false { "32-bit" }
}
"This version of Windows is $WinVer"I too, looked for a better answer, and while the solution in Edward's post is "ok", I came up with a far more natural solution in this blog post
Short and sweet:
# ---------------------------------------------------------------------------
# Name: Invoke-Assignment
# Alias: =
# Author: Garrett Serack (@FearTheCowboy)
# Desc: Enables expressions like the C# operators:
# Ternary:
# <condition> ? <trueresult> : <falseresult>
# e.g.
# status = (age > 50) ? "old" : "young";
# Null-Coalescing
# <value> ?? <value-if-value-is-null>
# e.g.
# name = GetName() ?? "No Name";
#
# Ternary Usage:
# $status == ($age > 50) ? "old" : "young"
#
# Null Coalescing Usage:
# $name = (get-name) ? "No Name"
# ---------------------------------------------------------------------------
# returns the evaluated value of the parameter passed in,
# executing it, if it is a scriptblock
function eval($item) { if( $item -ne $null ) { if( $item -is "ScriptBlock" ) { return & $item } return $item } return $null
}
# an extended assignment function; implements logic for Ternarys and Null-Coalescing expressions
function Invoke-Assignment { if( $args ) { # ternary if ($p = [array]::IndexOf($args,'?' )+1) { if (eval($args[0])) { return eval($args[$p]) } return eval($args[([array]::IndexOf($args,':',$p))+1]) } # null-coalescing if ($p = ([array]::IndexOf($args,'??',$p)+1)) { if ($result = eval($args[0])) { return $result } return eval($args[$p]) } # neither ternary or null-coalescing, just a value return eval($args[0]) } return $null
}
# alias the function to the equals sign (which doesn't impede the normal use of = )
set-alias = Invoke-Assignment -Option AllScope -Description "FearTheCowboy's Invoke-Assignment."Which makes it easy to do stuff like (more examples in blog post):
$message == ($age > 50) ? "Old Man" :"Young Dude" As of PowerShell version 7, the ternary operator is built into PowerShell.
1 -gt 2 ? "Yes" : "No"
# Returns "No"
1 -gt 2 ? 'Yes' : $null
# Get a $null response for false-y return valueSince a ternary operator is usually used when assigning value, it should return a value. This is the way that can work:
$var=@("value if false","value if true")[[byte](condition)]Stupid, but working. Also this construction can be used to quickly turn an int into another value, just add array elements and specify an expression that returns 0-based non-negative values.
1The ternary operator in PowerShell was introduced with the PowerShell version7.0.
[Condition] ? (output if True) : (output if False)Example 01
$a = 5; $b = 6
($a -gt $b) ? "True" : "False"Output
FalseExample 02
($a -gt $b) ? ("$a is greater than $b") : ("$a is less than $b")Output
5 is less than 6more information
Since I have used this many times already and didn't see it listed here, I'll add my piece :
$var = @{$true="this is true";$false="this is false"}[1 -eq 1]
ugliest of all !
4I've recently improved (open PullRequest) the ternary conditional and null-coalescing operators in the PoweShell lib 'Pscx'
Pls have a look for my solution.
My github topic branch: UtilityModule_Invoke-Operators
Functions:
Invoke-Ternary
Invoke-TernaryAsPipe
Invoke-NullCoalescing
NullCoalescingAsPipeAliases
Set-Alias :?: Pscx\Invoke-Ternary -Description "PSCX alias"
Set-Alias ?: Pscx\Invoke-TernaryAsPipe -Description "PSCX alias"
Set-Alias :?? Pscx\Invoke-NullCoalescing -Description "PSCX alias"
Set-Alias ?? Pscx\Invoke-NullCoalescingAsPipe -Description "PSCX alias"Usage
<condition_expression> |?: <true_expression> <false_expression>
<variable_expression> |?? <alternate_expression>As expression you can pass:
$null, a literal, a variable, an 'external' expression ($b -eq 4) or a scriptblock {$b -eq 4}
If a variable in the variable expression is $null or not existing, the alternate expression is evaluated as output.
0PowerShell currently doesn't didn't have a native Inline If (or ternary If) but you could consider to use the custom cmdlet:
IIf <condition> <condition-is-true> <condition-is-false>See: PowerShell inline If (IIf)
4If you're just looking for a syntactically simple way to assign/return a string or numeric based on a boolean condition, you can use the multiplication operator like this:
"Condition is "+("true"*$condition)+("false"*!$condition)
(12.34*$condition)+(56.78*!$condition)If you're only ever interested in the result when something is true, you can just omit the false part entirely (or vice versa), e.g. a simple scoring system:
$isTall = $true
$isDark = $false
$isHandsome = $true
$score = (2*$isTall)+(4*$isDark)+(10*$isHandsome)
"Score = $score"
# or
# "Score = $((2*$isTall)+(4*$isDark)+(10*$isHandsome))"Note that the boolean value should not be the leading term in the multiplication, i.e. $condition*"true" etc. won't work.
Here's an alternative custom function approach:
function Test-TernaryOperatorCondition { [CmdletBinding()] param ( [Parameter(ValueFromPipeline = $true, Mandatory = $true)] [bool]$ConditionResult , [Parameter(Mandatory = $true, Position = 0)] [PSObject]$ValueIfTrue , [Parameter(Mandatory = $true, Position = 1)] [ValidateSet(':')] [char]$Colon , [Parameter(Mandatory = $true, Position = 2)] [PSObject]$ValueIfFalse ) process { if ($ConditionResult) { $ValueIfTrue } else { $ValueIfFalse } }
}
set-alias -Name '???' -Value 'Test-TernaryOperatorCondition'Example
1 -eq 1 |??? 'match' : 'nomatch'
1 -eq 2 |??? 'match' : 'nomatch'Differences Explained
- Why is it 3 question marks instead of 1?
- The
?character is already an alias forWhere-Object. ??is used in other languages as a null coalescing operator, and I wanted to avoid confusion.
- The
- Why do we need the pipe before the command?
- Since I'm utilising the pipeline to evaluate this, we still need this character to pipe the condition into our function
- What happens if I pass in an array?
- We get a result for each value; i.e.
-2..2 |??? 'match' : 'nomatch'gives:match, match, nomatch, match, match(i.e. since any non-zero int evaluates totrue; whilst zero evaluates tofalse). - If you don't want that, convert the array to a bool;
([bool](-2..2)) |??? 'match' : 'nomatch'(or simply:[bool](-2..2) |??? 'match' : 'nomatch')
- We get a result for each value; i.e.
