In PowerShell, how can I test if a variable holds a numeric value?

Question

In PowerShell, how can I test if a variable holds a numeric value?

Currently, I\'m trying to do it like this, but it always seems to return false.

Answer 1

You can do something like :

$testvar -match '^[0-9]+$'

or

$testvar -match '^\d+$'

Returns True if $testvar is a number.

Answer 2

I ran into this topic while working on input validation with read-host. If I tried to specify the data type for the variable as part of the read-host command and the user entered something other than that data type then read-host would error out. This is how I got around that and ensured that the user enters the data type I wanted:

do
    {
    try
        {
        [int]$thing = read-host -prompt "Enter a number or else"
        $GotANumber = $true
        }
    catch
        {
        $GotANumber = $false
        }
    }
until
    ($gotanumber)

Answer 3

"-123.456e-789" -match "^\-?(\d+\.?\d*)(e\-?\d+)?$|^0x[0-9a-f]+$"

or

"0xab789" -match "^\-?(\d+\.?\d*)(e\-?\d+)?$|^0x[0-9a-f]+$"

will check for numbers (integers, floats and hex).

Please note that this does not cover the case of commas/dots being used as separators for thousands.

Answer 4

$itisint=$true
try{
 [int]$vartotest
}catch{
 "error converting to int"
 $itisint=$false
}

this is more universal, because this way you can test also strings (read from a file for example) if they represent number. The other solutions using -is [int] result in false if you would have "123" as string in a variable. This also works on machines with older powershell then 5.1

Answer 5

-is and -as operators requires a type you can compare against. If you're not sure what the type might be, try to evaluate the content (partial type list):

(Invoke-Expression '1.5').GetType().Name -match 'byte|short|int32|long|sbyte|ushort|uint32|ulong|float|double|decimal'

Good or bad, it can work against hex values as well (Invoke-Expression '0xA' ...)

Answer 6

Testing if a value is numeric or a string representation of a numeric value.

function Test-Number 
{
    Param
    (
        [Parameter(Mandatory=$true,
                   Position=0)]
        [ValidatePattern("^[\d\.]+$")]
        $Number
    )

    $Number -is [ValueType] -or [Double]::TryParse($Number,[ref]$null)
}

Testing if a value is numeric.

function Test-Number 
{
    Param
    (
        [Parameter(Mandatory=$true,
                   Position=0)]
        [ValidatePattern("^[\d\.]+$")]
        $Number
    )

    $Number -is [ValueType]
}