Use regex in Powershell v2 to get values from a json file - regex

Question

How would I access the following values using the regex function in Powershell, and assign each one to an individual variable?:
id (i.e. get the value: TOKEN_ID) - under token
id (i.e. get the value: TENANT_ID) - under token, tenant
adminURL (i.e. get the value: http://10.100.0.222:35357/v2.0) - the first value under serviceCatalog,endpoints
As I am using Powershell v2, I can't use the ConvertFrom-Json cmdlet. So far I've tried converting the document to an xml file using the a third-party PS script, but it doesn't always get it right. I'd like to use regex, but I am not very comfortable with it.
$json =
"{
"access": {
"metadata": {
"is_admin": 0,
"roles": [
"9fe2ff9ee4384b1894a90878d3e92bab"
]
},
"serviceCatalog": [
{
"endpoints": [
{
"adminURL": "http://10.100.0.222:8774/v2/TENANT_ID",
"id": "0eb78b6d3f644438aea327d9c57b7b5a",
"internalURL": "http://10.100.0.222:8774/v2/TENANT_ID",
"publicURL": "http://8.21.28.222:8774/v2/TENANT_ID",
"region": "RegionOne"
}
],
"endpoints_links": [],
"name": "nova",
"type": "compute"
},
{
"endpoints": [
{
"adminURL": "http://10.100.0.222:9696/",
"id": "3f4b6015a2f9481481ca03dace8acf32",
"internalURL": "http://10.100.0.222:9696/",
"publicURL": "http://8.21.28.222:9696/",
"region": "RegionOne"
}
],
"endpoints_links": [],
"name": "neutron",
"type": "network"
},
{
"endpoints": [
{
"adminURL": "http://10.100.0.222:8776/v2/TENANT_ID",
"id": "16f6416588f64946bdcdf4a431a8f252",
"internalURL": "http://10.100.0.222:8776/v2/TENANT_ID",
"publicURL": "http://8.21.28.222:8776/v2/TENANT_ID",
"region": "RegionOne"
}
],
"endpoints_links": [],
"name": "cinder_v2",
"type": "volumev2"
},
{
"endpoints": [
{
"adminURL": "http://10.100.0.222:8779/v1.0/TENANT_ID",
"id": "be48765ae31e425cb06036b1ebab694a",
"internalURL": "http://10.100.0.222:8779/v1.0/TENANT_ID",
"publicURL": "http://8.21.28.222:8779/v1.0/TENANT_ID",
"region": "RegionOne"
}
],
"endpoints_links": [],
"name": "trove",
"type": "database"
},
{
"endpoints": [
{
"adminURL": "http://10.100.0.222:9292",
"id": "1adfcb5414304f3596fb81edb2dfb514",
"internalURL": "http://10.100.0.222:9292",
"publicURL": "http://8.21.28.222:9292",
"region": "RegionOne"
}
],
"endpoints_links": [],
"name": "glance",
"type": "image"
},
{
"endpoints": [
{
"adminURL": "http://10.100.0.222:8777",
"id": "350f3b91d73f4b3ab8a061c94ac31fbb",
"internalURL": "http://10.100.0.222:8777",
"publicURL": "http://8.21.28.222:8777",
"region": "RegionOne"
}
],
"endpoints_links": [],
"name": "ceilometer",
"type": "metering"
},
{
"endpoints": [
{
"adminURL": "http://10.100.0.222:8000/v1/",
"id": "2198b0d32a604e75a5cc1e13276a813d",
"internalURL": "http://10.100.0.222:8000/v1/",
"publicURL": "http://8.21.28.222:8000/v1/",
"region": "RegionOne"
}
],
"endpoints_links": [],
"name": "heat-cfn",
"type": "cloudformation"
},
{
"endpoints": [
{
"adminURL": "http://10.100.0.222:8776/v1/TENANT_ID",
"id": "7c193c4683d849ca8e8db493722a4d8c",
"internalURL": "http://10.100.0.222:8776/v1/TENANT_ID",
"publicURL": "http://8.21.28.222:8776/v1/TENANT_ID",
"region": "RegionOne"
}
],
"endpoints_links": [],
"name": "cinder",
"type": "volume"
},
{
"endpoints": [
{
"adminURL": "http://10.100.0.222:8773/services/Admin",
"id": "11fac8254be74d7d906110f0069e5748",
"internalURL": "http://10.100.0.222:8773/services/Cloud",
"publicURL": "http://8.21.28.222:8773/services/Cloud",
"region": "RegionOne"
}
],
"endpoints_links": [],
"name": "nova_ec2",
"type": "ec2"
},
{
"endpoints": [
{
"adminURL": "http://10.100.0.222:8004/v1/TENANT_ID",
"id": "38fa4f9afce34d4ca0f5e0f90fd758dd",
"internalURL": "http://10.100.0.222:8004/v1/TENANT_ID",
"publicURL": "http://8.21.28.222:8004/v1/TENANT_ID",
"region": "RegionOne"
}
],
"endpoints_links": [],
"name": "heat",
"type": "orchestration"
},
{
"endpoints": [
{
"adminURL": "http://10.100.0.222:35357/v2.0",
"id": "256cdf78ecb04051bf0f57ec11070222",
"internalURL": "http://10.100.0.222:5000/v2.0",
"publicURL": "http://8.21.28.222:5000/v2.0",
"region": "RegionOne"
}
],
"endpoints_links": [],
"name": "keystone",
"type": "identity"
}
],
"token": {
"audit_ids": [
"gsjrNoqFSQeuLUo0QeJprQ"
],
"expires": "2014-12-15T15:09:29Z",
"id": "TOKEN_ID",
"issued_at": "2014-12-15T14:09:29.794527",
"tenant": {
"description": "Auto created account",
"enabled": true,
"id": "TENANT_ID",
"name": "USERNAME"
}
},
"user": {
"id": "USER_ID",
"name": "USERNAME",
"roles": [
{
"name": "_member_"
}
],
"roles_links": [],
"username": "USERNAME"
}
}
}"

Answer 1

If you are using .NET 3.5 or higher on your machines with PowerShell 2.0, you can use a JSON serializer (from the linked answer):
[System.Reflection.Assembly]::LoadWithPartialName("System.Web.Extensions")
$json = "{a:1,b:2,c:{nested:true}}"
$ser = New-Object System.Web.Script.Serialization.JavaScriptSerializer
$obj = $ser.DeserializeObject($json)
This would be preferable to using regex.
For admin URL for example, you'd refer to:
$obj.access.serviceCatalog[0].endpoints[0].adminURL
Using RegEx Anyway
if ($json -match '(?s)"serviceCatalog".+?"endpoints".+?"adminURL"[^"]+"(?<adminUrl>[^"]+)".+?"token".+?"id"[^"]+"(?<tokenID>[^"]+)".+?"tenant".+?"id"[^"]+"(?<tenantID>[^"]+)') {
$Matches['adminURL']
$Matches['tokenID']
$Matches['tenantID']
}
RegEx Breakdown:
(?s) tells the regex engine that . matches anything, including newlines (by default it wouldn't).
Of course all of the "whatever" parts just match literally.
.+? matches 1 or more of any character (including newlines since we're using s), and the ? makes it non-greedy.
[^"]+ this matches 1 or more characters that are not a double quote.
() is a capturing group. By using (?<name>) we can refer back to the group later by name rather than number, just a nicety.
So the basic idea is to look for the literals, then get to a point where we can capture the values needed. After a -regex operator match in PowerShell, the $Matches variable is populated with the matches, groups, etc.
Note that this relies on the values being in the order they are in the posted JSON. If they were in a different order it would fail.
To work around that you could split this into 3 different regex matches.