How do I get a list of Amazon regions via the command line?

This is now how you'd do it using the aws cli:

$ aws ec2 describe-regions --output table
----------------------------------------------------------
|                     DescribeRegions                    |
+--------------------------------------------------------+
||                        Regions                       ||
|+-----------------------------------+------------------+|
||             Endpoint              |   RegionName     ||
|+-----------------------------------+------------------+|
||  ec2.eu-west-1.amazonaws.com      |  eu-west-1       ||
||  ec2.ap-southeast-1.amazonaws.com |  ap-southeast-1  ||
||  ec2.ap-southeast-2.amazonaws.com |  ap-southeast-2  ||
||  ec2.eu-central-1.amazonaws.com   |  eu-central-1    ||
||  ec2.ap-northeast-2.amazonaws.com |  ap-northeast-2  ||
||  ec2.ap-northeast-1.amazonaws.com |  ap-northeast-1  ||
||  ec2.us-east-1.amazonaws.com      |  us-east-1       ||
||  ec2.sa-east-1.amazonaws.com      |  sa-east-1       ||
||  ec2.us-west-1.amazonaws.com      |  us-west-1       ||
||  ec2.us-west-2.amazonaws.com      |  us-west-2       ||
|+-----------------------------------+------------------+|

You can do this by running the command ec2-describe-regions from the command line (if you have ec2-api-tools installed available in multiverse).

$ ec2-describe-regions
REGION  eu-west-1   ec2.eu-west-1.amazonaws.com
REGION  sa-east-1   ec2.sa-east-1.amazonaws.com
REGION  us-east-1   ec2.us-east-1.amazonaws.com
REGION  ap-northeast-1  ec2.ap-northeast-1.amazonaws.com
REGION  us-west-2   ec2.us-west-2.amazonaws.com
REGION  us-west-1   ec2.us-west-1.amazonaws.com
REGION  ap-southeast-1  ec2.ap-southeast-1.amazonaws.com