i need to integrate some feature of infusionsoft. how can i authenticate via api in REST without displaying granting permission ? please help me out 
Are you attempting to write a script for you own use with your single application, or provide an application to support multiple consumers?
- In the first case you can use the Accounts page to generate a token, and just maintain that perpetually.
- In the latter case, you will need to provide a public-facing OAuth receiver endpoint to get access to the user’s application data.