The present invention provides a computer implemented method and apparatus for a built-in function of a shell to execute in a thread of an interactive shell process. The data processing system receives a request to execute the built-in function. The data processing system determines that the request includes a thread creating indicator. The data processing system schedules a thread to execute the built-in function, in response to a determination that the request includes the thread creating indicator, wherein the thread is controlled by the interactive shell process and shares an environment of the interactive shell process. The data processing system declares a variable based on at least one instruction of the built-in function. Finally, the data processing system may access the variable.