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

Question

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

add-type -Language CSharpVersion3 @'
    public class Helpers {
        public static bool IsNumeric(object o) {
            return o is byte  || o is short  || o is int  || o is long
                || o is sbyte || o is ushort || o is uint || o is ulong
                || o is float || o is double || o is decimal
                ;
        }
    }
'@

filter isNumeric($InputObject) {
    [Helpers]::IsNumeric($InputObject)
}

PS> 1 | isNumeric
False

score 57 · Answer 1 · answered Jun 07 '12 at 08:16

57

You can check whether the variable is a number like this: $val -is [int]

This will work for numeric values, but not if the number is wrapped in quotes:

1 -is [int]
True
"1" -is [int]
False

answered Jun 07 '12 at 08:16

tophatsteve

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@Christian you're right. I was only thinking about the case in the question. – tophatsteve Jun 07 '12 at 08:29
4

@CB that's because `1.5` is not an integer, it is a double... `1.5 -is [double]` evaluates to true – Kellen Stuart Oct 04 '17 at 18:54
1

Also fails if the value is cast as a Int64. – Jim Jan 26 '23 at 18:33

score 42 · Answer 2 · answered Jun 07 '12 at 20:46

42

If you are testing a string for a numeric value then you can use the a regular expression and the -match comparison. Otherwise Christian's answer is a good solution for type checking.

function Is-Numeric ($Value) {
    return $Value -match "^[\d\.]+$"
}

Is-Numeric 1.23
True
Is-Numeric 123
True
Is-Numeric ""
False
Is-Numeric "asdf123"
False

answered Jun 07 '12 at 20:46

joshuapoehls

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1

I'm not testing a string, I'm testing a type. But ignoring that for the moment, how about negative values? And what about exponential values (3.24643e4)? Yeah, I know, I'm splitting hairs! – Damian Powell Jun 08 '12 at 14:42
2

I'll leave that as an exercise for the reader. :) I just wanted to add this for people who may stumble on the question looking for checking numeric string values. – joshuapoehls Jun 08 '12 at 15:10
1

Well done @silent__thought, I was looking for exactly this. – Tim Meers Aug 10 '16 at 18:17
`"1.2.3" -match "^[\d\.]+$"` --> True. `"^(\d+|\.\d+|\d+\.\d+)$"` would allow only one decimal separator. Returns true for "1", ".1", "1.1" and false for "1.", "1.1.1", "". – jumxozizi Jul 06 '18 at 12:51
this regex is incorrect, `Is-Numeric .................` would be true – Santiago Squarzon Jan 18 '23 at 00:01

score 33 · Answer 3 · edited Sep 05 '19 at 21:04

33

You can do something like :

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

or

$testvar -match '^\d+$'

Returns True if $testvar is a number.

edited Sep 05 '19 at 21:04

Dan Atkinson

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answered May 10 '17 at 11:06

Matt

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This will only return true for positive integers – Marc Jul 01 '22 at 14:13

score 31 · Accepted Answer · edited Sep 03 '22 at 18:04

31

Modify your filter like this:

filter isNumeric {
    [Helpers]::IsNumeric($_)
}

function uses the $input variable to contain pipeline information whereas the filter uses the special variable $_ that contains the current pipeline object.

Edit:

For a powershell syntax way you can use just a filter (w/o add-type):

filter isNumeric($x) {
    return $x -is [byte]  -or $x -is [int16]  -or $x -is [int32]  -or $x -is [int64]  `
       -or $x -is [sbyte] -or $x -is [uint16] -or $x -is [uint32] -or $x -is [uint64] `
       -or $x -is [float] -or $x -is [double] -or $x -is [decimal]
}

edited Sep 03 '22 at 18:04

ndemou

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answered Jun 07 '12 at 08:20

CB.

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I think the native PowerShell route is the way I'll go. Thanks, @Christian. – Damian Powell Jun 07 '12 at 17:13
3

Unable to find type [Helpers] – McVitas May 21 '20 at 20:08
This is the first answer that really tests if a variable holds a numeric value. All others test if a _string_ represents a numeric value – ndemou Sep 03 '22 at 18:06

score 17 · Answer 5 · answered Dec 09 '14 at 10:17

17

If you want to check if a string has a numeric value, use this code:

$a = "44.4"
$b = "ad"
$rtn = ""
[double]::TryParse($a,[ref]$rtn)
[double]::TryParse($b,[ref]$rtn)

Credits go here

answered Dec 09 '14 at 10:17

tsap

803
8
10

score 12 · Answer 6 · edited Oct 22 '12 at 07:35

12

PS> Add-Type -Assembly Microsoft.VisualBasic
PS> [Microsoft.VisualBasic.Information]::IsNumeric(1.5)
True

http://msdn.microsoft.com/en-us/library/microsoft.visualbasic.information.isnumeric.aspx

edited Oct 22 '12 at 07:35

Ocaso Protal

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answered Jun 07 '12 at 16:20

x0n

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1

I thought this was pretty neat until I realised that it would return true for a string that was numeric such as `"1.23"` which is not what I want. I want to know if the type of the actual object is a numeric type, not whether or not it can be coerced to a numeric type. Thanks for a useful tip though, I can see where that will be very handy. – Damian Powell Jun 07 '12 at 17:12

Shay Levy · Answer 7 · 2012-06-07T09:01:36.707

10

-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' ...)

edited Jun 07 '12 at 09:01

answered Jun 07 '12 at 08:46

Shay Levy

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That's a neat solution. For the context I need to use it though, `Invoke-Expression` could be quite dodgy! – Damian Powell Jun 08 '12 at 14:48
2

Try{(Invoke-Expression '-123s.456e-789 ').GetType().Name -match 'byte|short|int32|long|sbyte|ushort|uint32|ulong|float|double|decimal'}Catch{$false}---Although you solution is almost perfect and flexible – Garric Aug 30 '20 at 04:50

Aaron · Answer 8 · 2017-04-02T23:34:39.910

6

filter isNumeric {
    $_ -is [ValueType]
}

-

1 -is [ValueType]
True
"1" -is [ValueType]
False

-

function isNumeric ($Value) {
    return $Value -is [ValueType]
}

isNumeric 1.23
True
isNumeric 123
True
isNumeric ""
False
isNumeric "asdf123"
False

-

(Invoke-Expression '1.5') -is [ValueType]

edited Apr 02 '17 at 23:34

answered Apr 02 '17 at 10:12

Aaron

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1

PS> [System.Reflection.BindingFlags]::CreateInstance -is [valuetype] (True) – x0n Aug 28 '18 at 14:10
2

PS> [char]"a" -is [valuetype] (True) – x0n Aug 28 '18 at 14:14
This is the right answer! – joeking Jul 08 '22 at 23:17
@x0n I don't know why but although your tests are ... true the function isNumeric correctly returns $false for both your cases. VERY strange but I'm also very tired. – ndemou Sep 03 '22 at 18:13
This is by far the best and most succinct PowerShell solution. Nicely done! – Jim Jan 26 '23 at 18:51

McVitas · Answer 9 · 2020-05-26T22:20:59.280

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

edited May 26 '20 at 22:20

answered May 21 '20 at 20:30

McVitas

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It’s always valuable to explain your code, but that’s especially true in a case like this where there’s a highly-rated accepted answer from eight years ago. Why is your approach preferred over the accepted answer? Do you mind updating your answer with more details? – Jeremy Caney May 22 '20 at 05:44
2

If you are using `Read-Host` the result is always a string so you need to perform a check to see if the input even *is* numeric before converting. Generating and catching exceptions as flow control is always bad due to the amount of stuff done behind the scenes. The powershell way would be `$converted = $myInput -as [int]`. `$converted` will be `$null` if it could not convert, or the number if it was successful – DreadedEntity Mar 05 '22 at 18:08

score 3 · Answer 10 · answered Jan 10 '13 at 20:55

3

Thank you all who contributed to this thread and helped me figure out how to test for numeric values. I wanted to post my results for how to handle negative numbers, for those who may also find this thread when searching...

Note: My function requires a string to be passed, due to using Trim().

function IsNumeric($value) {
# This function will test if a string value is numeric
#
# Parameters::
#
#   $value   - String to test
#
   return ($($value.Trim()) -match "^[-]?[0-9.]+$")
}

answered Jan 10 '13 at 20:55

edwdecarlo

47
3

7

This will return true for version numbers like "9.3.4", you'd be better served by a regex like `^[-+]?([0-9]*\.[0-9]+|[0-9]+\.?)$` which will validate you have only an optional plus/minus; numbers and an single optional decimal point. – Ro Yo Mi Apr 03 '14 at 20:39

dan-gph · Answer 11 · 2023-01-17T23:58:39.747

3

If you know the numeric type you want to test against (such as int for example in the code below), you can do it like this:

> [bool]("42" -as [int])
True
> [bool](42 -as [int])
True
> [bool]("hi" -as [int])
False

But note:

> [bool](42.1 -as [int])
True

Careful!:

It was pointed out that the code above fails to identify 0 as an int. You would need to add a guard for 0:

> $n -eq 0 -or $n -as [int]

Where $n is the object you are testing.

edited Jan 17 '23 at 23:58

answered Oct 06 '22 at 09:21

dan-gph

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12
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I like this one. Or `'11' | where { $(if ($_ -as 'int') { 10 -le $_ }) }` – js2010 Nov 13 '22 at 18:00
Unfortunately: `[bool](0 -as [int])` is `False`. – Hank Schultz Jan 16 '23 at 18:30
1

@HankSchultz thanks. That is a good bug to find. I have added a note at the end. – dan-gph Jan 17 '23 at 23:59

score 2 · Answer 12 · answered Jan 06 '17 at 18:42

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)

Jens Bonnermann · Answer 13 · 2020-01-08T16:20:26.640

1

"-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.

edited Jan 08 '20 at 16:20

answered Jan 06 '20 at 21:19

Jens Bonnermann

11
5

score 1 · Answer 14 · answered Aug 18 '20 at 10:20

Each numeric type has its own value. See TypeCode enum definition: https://learn.microsoft.com/en-us/dotnet/api/system.typecode?view=netframework-4.8 Based on this info, all your numeric type-values are in the range from 5 to 15. This means, you can write the condition-check like this:

$typeValue = $x.getTypeCode().value__
if ($typeValue -ge 5 -and $typeValue -le 15) {"x has a numeric type!"}

score 0 · Answer 15 · answered Feb 18 '17 at 02:40

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]
}

`$n=0; [Double]::TryParse('1e2', [ref]$n)` will parse it as a string representation of a number, but your functions will fail it. Same with negative numbers. — TessellatingHeckler, Feb 18 '17 at 03:24

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

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