Where could i lookup my AccountID and ExtensionID

Does this API endpoint grab all extensions and account id's for all rc users or is it for the user logged in?  It seems that it works on a per/user basis since the main argument is the tilde which, as I understand it, is only for the currently logged in user.  Therefore, if I understand the endpoint summary correctly, it will grab all extensions and the account id for the logged in user but not all users.  Is that the case?

Does this API endpoint grab all extensions and account id's for all rc users or is it for the user logged in?  

One or more extensions exist under an Account. Lets say you have an Account named 'A' and all the extensions under this account would look like as below :

Account A

• Ext 101 or User 1

• Ext 102 or User 2

• Ext 103 or User 3 etc

So irrespective of the User that you are authorizing as, the Get Extensions ( API Endpoint ) would retrieve all the extensions which belong to the account ( Account A )
 
Below is the sample API Request and response :

API Request

GET /v1.0/account/{accountId}/extension

Note: The {accountId} == ~ would refer to the account to whihc the extension belongs to.

API Response

{
  "uri": "https://platform.ringcentral.com/restapi/v1.0/account/1234567/extension?page=1&perPage=100&quo...;,
  "records": [
    {
      "uri": "https://platform.ringcentral.com/restapi/v1.0/account/1234567/extension/1024935020";,
      "id": "<<extensionID for 101>>",
      "extensionNumber": "101",
      "contact": {
        "firstName": "Extension number 101",
        "email": "sample.test@company.com",
        "pronouncedName": {
          "type": "Default"
        }
      },
      "name": "Message-Only-Extension",
      "type": "Voicemail",
      "status": "Enabled",
      "permissions": {
        "admin": {
          "enabled": false
        },
        "internationalCalling": {
          "enabled": false
        }
      },
      "profileImage": {
        "uri": "https://platform.ringcentral.com/restapi/v1.0/account/1234567/extension/1024935020";
      }
    },
    {
      "uri": "https://platform.ringcentral.com/restapi/v1.0/account/1234567/extension/1024935020";,
      "id": "<<extensionID for 102>>"
      "extensionNumber": "102",
      "contact": {
        "firstName": "Extension name for ",
        "lastName": "Notification",
        "company": "RC",
        "email": "sample.test@company.com",
        "emailAsLoginName": true,
        "pronouncedName": {
          "type": "TextToSpeech"
        }
      },
      "name": "AWS Notification",
      "type": "User",
      "status": "Enabled",
      "permissions": {
        "admin": {
          "enabled": false
        },
        "internationalCalling": {
          "enabled": true
        }
      },
      "profileImage": {
        "uri": "https://platform.ringcentral.com/restapi/v1.0/account/1234567/extension/1024935020";,
      }
    },
}

Thanks for the detailed response.  If I understand you correctly, and what I assumed, was that the api will retrieve all extensions for a single user, respectively the one logged in and running the get extension api call.  

Here is my scenario:  I have written an automated process that will need to go and check each of our ring central users one by one and all their associated extensions for messages and attachments and download them to our servers here locally for use in our business processes.  This automated process would need to cycle through all user accounts to do this so no one individual will be logged in.  Rather a super account would be running this process and retrieving the data.  Is it possible to do this?  All I need are all the account ids for each of our uses but in order to do this it seems that I'd have to run the api (via the code I've written as and installed service on each system) from each users machine under their id to get that account.  All I need is a list of the account ids to have my automated process cycle through and retrieve the data but it doesn't seem to be possible unless I have the process run from each user's machine under their id and retrieve that data.

Based on what you wrote above, it seems like you have an app that connects to multiple RingCentral and you want to retrieve data for each account.

To this you need the following at a high level:

• A public app as a private app can only connect to the owner's account, not other accounts. In the Developer Portal, ensure your app's scope is set to Public.
• A UI that uses RingCentral's 3-legged OAuth 2.0 authorization flow, either the Authorization Code or Implicit Grant flow. To retrieve data for all users in an account, you either need (a) an admin to authorize your app for each account or (b) each user to authorize your app.
• After the user authorizes the account, you will receive an access token representing that user's authorization of your app. At this point you can retrieve a list of all user extensions from the account extension endpoint: /restapi/v1.0/account/~/extension . Technically, you do not need to explicitly use the accountId in API calls since the "~" shorthand notation will represent the current account for the access token, but if you want it, you can retrieve the accountId from the /restapi/v1.0/account/~ endpoint.
• With an access token for each account, just cycle through the accounts and each account's extensions.

Here are some more detailed steps on how to accomplish this : 

• Authorization Code Flow using OAuth2.0 : 

          The app would need to support the OAuth2.0 Authentication flow by which you           can authenticate users on your app. To know more on how to implement the              Authorization Code Flow inside your application read below :

https://devcommunity.ringcentral.com/ringcentraldev/topics/using-oauth-2-0-          authorization-code-grant-...

• Get Accound ID :

          Get Company Info ( API Endpoint )

          Per this API endpoint, you would need to provide tilde (~) to get the account                 information as below :

          /v1.0/account/{accountId}

• Get all Extensions under the account :

         Once you have the accountId, you can obtain the all the extensions that belong          to that account using the :

         Get Extensions ( API Endpoint ) 

Benefits of Implementing this architecture :

• No need to run the process from each users machine
• A consistent and trusted UI
• Integrated password reset
• Integrated single sign-on (SSO) via SAML support