Conditionals: if, elseif, else

$temperature = 18

if ($temperature -gt 25) {
  'It is hot'
} elseif ($temperature -gt 15) {
  'It is pleasant'
} else {
  'It is cold'
}

It is pleasant

• The condition goes in parentheses; the code in braces.
• Only the first matching branch runs.
• Leaving a string on its own line outputs it — the same as Write-Output.

What counts as true

Values are converted to $true or $false in conditions:

$tests = [ordered]@{
  '0' = 0; '1' = 1; "''" = ''; "'text'" = 'text'
  '$null' = $null; '@()' = @(); '@(0)' = @(0)
}
foreach ($test in $tests.GetEnumerator()) {
  '{0,-8} -> {1}' -f $test.Key, [bool]$test.Value
}

0        -> False
1        -> True
''       -> False
'text'   -> True
$null    -> False
@()      -> False
@(0)     -> False

0, empty strings, $null, and empty arrays are false. Surprisingly, an array containing a single 0 is also false, because PowerShell looks at the one element. Test explicitly when it matters: if ($list.Count -gt 0).

if returns a value

$age = 20
$status = if ($age -ge 18) { 'adult' } else { 'minor' }
$status

adult

(In PowerShell 7, the ternary operator does the same: $age -ge 18 ? 'adult' : 'minor'.)

Practice

Store an age and output adult for 18 and over, teen for 13–17, and child otherwise.

$age = 15
if ($age -ge 18) { 'adult' }
elseif ($age -ge 13) { 'teen' }
else { 'child' }

teen