Regex for string following a string and forward slash

Question

I'm trying to extract the resource group name in Azure via az cli.

The full path to a certain resource group looks like this:

/subscriptions/b049-1234-1256-125456-125/resourceGroups/Test_ResourceGroup

I'm trying to only extract "Test_ResourceGroup" out of the full string (which is stored in a variable), so i think the code would be something like

$scope = /subscriptions/b049-1234-1256-125456-125/resourceGroups/Test_ResourceGroup
$resourcegroup = $scope -match 'regex'

But I'm terrible at regex and not great at it. The addition challenge is that sometimes there's more strings or integers after the resource name, e.g.

/subscriptions/b049-1234-1256-125456-125/resourceGroups/Test_ResourceGroup/specificnameofresource/blahblah

But again, I just want the resource group name.

how do you decide what is the resource group name in the 2nd string? — Lee_Dailey, May 11 '20 at 03:02
I expect you mean what to extract the string following the literal "/resourceGroups/" up to the next forward slash or the end of the line or string. Correct? I believe Powershell supports lookaheads and (fixed-length) lookbehinds, in which you could match `(?<=\/resourceGroups\/)[^\/]+`. [Demo](https://regex101.com/r/OT7jaK/2/). `(?<=\/resourceGroups\/)` is a *positive lookbehind*, which must be matched but is not part of the match returned. `[^\/]+` gobbles up characters other than forward slashes until it reaches a forward slash or the end of the string. — Cary Swoveland, May 11 '20 at 03:12

score 0 · Answer 1 · answered May 11 '20 at 03:37

while a pure regex solution is likely faster, this is simpler & easier to understand/modify. well, it is for me. [grin]

the neat thing is that the final .Split() will silently fail, so it works for "end of string" and for any position in the string.

$TestList = @(
    '/subscriptions/b049-1234-1256-125456-125/resourceGroups/Test_ResourceGroup/specificnameofresource/blahblah'
    '/subscriptions/b049-1234-1256-125456-125/resourceGroups/ResourceGroupZiggity'
    )

foreach ($TL_Item in $TestList)
    {
    ($TL_Item -split 'resourcegroups/')[-1].Split('/')[0]
    }

output ...

Test_ResourceGroup
ResourceGroupZiggity

score 0 · Answer 2 · answered May 11 '20 at 07:03

You can use the regex-based -replace operator:

$resourcegroup = $scope -replace '.+/resourceGroups/([^/]+).*', '$1'

.+/resourceGroups/ captures one or more (+) characters (.), followed by /resourceGroups/, i.e. everything up to and including /resourceGroups/.
[^/]+ captures one or more characters that are not (^) in the character set ([...]) comprising /, i.e. everything up, but not including the next /, if any.
(...) is a capturing subexpression a so-called capture group), whose captured text can be referred to in the replacement operand (substitution text) as $1.
.* matches zero or more (*) remaining characters, i.e. whatever characters are left.
Since the regex matches the entire input string, replacing what it matched with '$1 in effect extracts just the token of interest.

Regex for string following a string and forward slash

2 Answers2