More RegEx confusion with telephone numbers

PowerShell Help
1

Hi all,

I have been asked to convert the UK telephones stored in AD in the E164 standard to the +44(0) XXX XXX XXX format by the business (which a lot of people do not like - not my decision).

As I do not know what the telephone numbers will be, but know the pattern, I thought this would be perfect for RegEx however am again struggling to get it to work.

The first issue is one of error checking.

I have created this RegEX expression to detect both formats:

#Example Format required by business
$a = "+44(0)1202 204 746"
#Example in E164 format
$b = "+441202204746"
#RegEx for $a
$a -match "^\+[44]*[(0)]*\d{4}\s*\d{3}\s*\d{3}$"
#RegEx for $b
$b -match "^\+[44][0-9]*$"

Unfortunately if I run the RegEx for $a on $b it will still come back true, so I cannot be sure that the number is in the correct format. How do I ensure the RegEx returns false if there are no spaces and (0) in the number?

The second one is how to alter the number. I have tried the following two methods, but neither are working. What am I doing wrong?

$a = "+441202204746"
$a -replace "(^\+[44]*[(0)]*\d{4}\s*\d{3}\s*\d{3}$)", '$a'
$a

$a = "4412022047"
$b = "{0:(###) ###-####}" -f $a
$b

Thanks in advance for any pointers you can give me :slight_smile:

2

In regex, square brackets create a character class, a set of characters that will be matched in a single position of the input string (unless you add a quantifier, such as + or * or {3} which tells it to match the character class a different number of times.)

If you don’t actually care what format the phone number was originally in, and just want to make sure it’s matching the “+44(0)1202 204 746” format, then this should work with a single pattern:

$numbers = @(
    '+44(0)1202 204 746'
    '+441203206748'
    '+4412345678901' # Deliberately has too many digits to test validation
)

$pattern = '^\+44(?:\(0\))?(\d{4})\s*(\d{3})\s*(\d{3})$'

foreach ($number in $numbers)
{
    if ($number -match $pattern)
    {
        '+44(0){0} {1} {2}' -f $matches[1], $matches[2], $matches[3]
    }
    else
    {
        Write-Error "Number '$number' is not a valid UK telephone number."
    }
}
3

Hi Dave,

Thanks for your reply. To make things easier, we are just going to check the telephone attribute currently in AD is in E164 format by using this RegEx (basically has a + and 12 digits with no spaces)

$b -match "^\+?\d{12}$"

and before we write to a custom AD attribute, check to see if they are an exact match rather than using RegEx.

The part I am still confused about is how the formatting works.

I have had a look at http://msdn.microsoft.com/en-us/library/System.String.Format(v=vs.110).aspx to better understand how this works, but I am still confused and I cannot get your example to work in another example.

If I understand correctly in the line

'+44(0){0} {1} {2}' -f $matches[1], $matches[2], $matches[3]

you are telling the formatting command to put into matches[1],[2] and [3] the relevant parts of the number, but I am struggling to see how. Is this because of the RegEx in $pattern?

Thanks again for all of your help!