Powershell get region from AWS metadata

Question

I have an EC2 instance and I am running a Powershell script there where I would like to get the region that the EC2 is running in.

Currently I have workaround like this which grabs the availability zone first. The availability zone is in the format like 'us-east-1a'.

$region = invoke-restmethod -uri http://169.254.169.254/latest/meta-data/placement/availability-zone 
if ($region -like "*east*") {$region = "us-east-1"} ELSE {$region = "us-west-2"} 

I would like to just grab the region, rather than get the availability zone and then do some modifications. I know there is a possibility to use:

http://169.254.169.254/latest/dynamic/instance-identity/document

This returns a JSON object which has the region, but I would also need to parse the JSON to achieve this.

How do I get just the region?

Answer 1

You can use ConvertFrom-Json :

PS C:\> $region = (Invoke-WebRequest -UseBasicParsing -Uri http://169.254.169.254/latest/dynamic/instance-identity/document | ConvertFrom-Json | Select region).region

edit: added -UseBasicParsing

Answer 2

Will this work?

PS C:\> $region = invoke-restmethod -uri http://169.254.169.254/latest/meta-data/placement/availability-zone

PS C:\> $region.Substring(0,$region.Length-1)

Answer 3

Parsing the availability-zone is not the safest way. Region name is available as an attribute of the Instance Identity Document, which is generated when the instance is launched. There are two options to read this information with Powershell:

You could use Invoke-WebRequest:

IWR (also aliased as curl and wget) works fine, but it can only deal with HTML. So you need an extra step to parse JSON. It uses the IE COM interface to parse the DOM by default, but you can avoid that with the -UseBasicParsing option.

PS C:\> curl http://169.254.169.254/latest/dynamic/instance-identity/document | ConvertFrom-Json | Select region

region
------
us-east-1

PS C:\> (curl http://169.254.169.254/latest/dynamic/instance-identity/document | ConvertFrom-Json).region
us-east-1

But Invoke-RestMethod is the best option:

Since this is a REST interface, IRM is the best choice because it natively supports JSON and XML.

PS C:\> irm http://169.254.169.254/latest/dynamic/instance-identity/document | Select region

region
------
us-east-1

PS C:\> (irm http://169.254.169.254/latest/dynamic/instance-identity/document).region
us-east-1

PS C:\> irm http://169.254.169.254/latest/dynamic/instance-identity/document | % region
us-east-1

Answer 4

Try using :

EC2_AVAIL_ZONE=`curl -s http://169.254.169.254/latest/meta-data/placement/availability-zone`
EC2_REGION="`echo \"$EC2_AVAIL_ZONE\" | sed -e 's:\([0-9][0-9]*\)[a-z]*\$:\\1:'`"

OR

EC2_INSTANCE_ID="`wget -q -O - http://169.254.169.254/latest/meta-data/instance-id || die \"wget instance-id has failed: $?\"`"test -n "$EC2_INSTANCE_ID" || die 'cannot obtain instance-id'

EC2_AVAIL_ZONE="`wget -q -O - http://169.254.169.254/latest/meta-data/placement/availability-zone || die \"wget availability-zone has failed: $?\"`"test -n "$EC2_AVAIL_ZONE" || die 'cannot obtain availability-zone'

EC2_REGION="`echo \"$EC2_AVAIL_ZONE\" | sed -e 's:\([0-9][0-9]*\)[a-z]*\$:\\1:'`"

JQ:

curl -s http://169.254.169.254/latest/dynamic/instance-identity/document | jq .region -r

Reference : Instance Metadata

Note: This has to be run from inside the EC2 instance because that IP is an APIPA. There is no way to get this information directly from inside the instance without connecting to a metadata source

Hope it helps

Answer 5

$region = Get-EC2InstanceMetadata -Category region

write-output "Get region:"

write-output $region.SystemName