Use PutGroupPolicy with an Amazon SDK or command line tool

    /// <summary>
    /// Add or update an inline policy document that is embedded in an IAM group.
    /// </summary>
    /// <param name="groupName">The name of the IAM group.</param>
    /// <param name="policyName">The name of the IAM policy.</param>
    /// <param name="policyDocument">The policy document defining the IAM policy.</param>
    /// <returns>A Boolean value indicating the success of the action.</returns>
    public async Task<bool> PutGroupPolicyAsync(string groupName, string policyName, string policyDocument)
    {
        var request = new PutGroupPolicyRequest
        {
            GroupName = groupName,
            PolicyName = policyName,
            PolicyDocument = policyDocument
        };

        var response = await _IAMService.PutGroupPolicyAsync(request);
        return response.HttpStatusCode == System.Net.HttpStatusCode.OK;
    }

To add a policy to a group

The following put-group-policy command adds a policy to the IAM group named Admins.

aws iam put-group-policy \
    --group-name Admins \
    --policy-document file://AdminPolicy.json \
    --policy-name AdminRoot

This command produces no output.

The policy is defined as a JSON document in the AdminPolicy.json file. (The file name and extension do not have significance.)

For more information, see Managing IAM policies in the Amazon IAM User Guide.

Example 1: This example creates an inline policy named AppTesterPolicy and embeds it in the IAM group AppTesters. If an inline policy with the same name already exists, then it is overwritten. The JSON policy content comes the file apptesterpolicy.json. Note that you must use the -Raw parameter to successfully process the content of the JSON file.

Write-IAMGroupPolicy -GroupName AppTesters -PolicyName AppTesterPolicy -PolicyDocument (Get-Content -Raw apptesterpolicy.json)