curl \
  -k \
  -s \
  -H "Accept: application/json" \
  --user caadmin:Secret.123 \
  https://localhost.localdomain:8443/ca/rest/admin/users | python -m json.tool
{
    "total": 3,
    "entries": [
        {
            "id": "CA-localhost.localdomain-8443",
            "UserID": "CA-localhost.localdomain-8443",
            "FullName": "CA-localhost.localdomain-8443",
            "Link": {
                "rel": "self",
                "href": "https://localhost.localdomain:8443/ca/rest/admin/users/CA-localhost.localdomain-8443",
                "type": "application/xml"
            },
            "Attributes": {
                "Attribute": []
            }
        },
        ...
    ],
    "Link": []
}