String is numeric?

by MasterOfTheHat at 2013-03-21 06:58:12

This morning I needed to filter through the results of a script I’ve written to return stale users in AD, and I needed to eliminate all users whose EmployeeID field was non-numeric. My first instinct was to look for a native posh equivalent of VB’s IsNumeric() function. Apparently, it doesn’t exist… What I did find was that several people recommended the following function as the best way to emulate IsNumeric().

Agree? Disagree? Other options? This function is simple and it does what I need it to, but it kind of surprises me that this is the best solution.

function isNumeric ($x) {
try {
0 + $x | Out-Null
return $true
} catch {
return $false
}
}
by bgenwell at 2013-03-21 07:01:24
I could see matching based on regex:

$user | ?{$.employeeid -notmatch “\d”}
by mjolinor at 2013-03-21 07:35:26
if ([string]($x -as [int]))

should have the same effect.
by MasterOfTheHat at 2013-03-21 09:49:06
After a small tweak to your code and a small tweak to my function, It looks like they’re doing the same thing:
function isNumeric ($x) {
if($x -eq $null)
{
return $false
}
try {
0 + $x | Out-Null
return $true
} catch {
return $false
}
}

PS > $staleUsers | % { “{0} - {1} - {2}” -f $
.EmployeeID, [bool]($.EmployeeID -as [int]), $(isNumeric($.EmployeeID)) }
7205 - 7205 - True
- 0 - False
- 0 - False
6872ATC - False - False
by Nobody at 2013-03-21 11:16:25
I was shown this way.

[void][reflection.assembly]::LoadWithPartialName("'Microsoft.VisualBasic")
$a = 1
[Microsoft.VisualBasic.Information]::isnumeric($a)


edit:
http://technet.microsoft.com/en-us/libr … 76889.aspx
by poshoholic at 2013-03-21 12:15:58
I’ve always just used a simple regex for this.
$x -match '^\d+$'
If that returns true, the string is a positive integer. Otherwise it returns false.

Here’s a version that supports negative and decimal values as well:
$x -match '^-?(.\d+|\d+(.\d*)?)$'
That’s messy though. If you really want support for negative integers and decimal values as well, you can simply check it like this:
$numericValue = $null
if (-not ([double]]$numericValue))) {
throw ‘Not a double!’
}

And of course you can use int instead of double or uint32 if you want an unsigned integer value, etc.
by MasterOfTheHat at 2013-03-21 13:07:36
About as many approaches as there are scripters… Thanks for the info, guys. At least it was a legitimate question and not something obvious that I’d just missed.