What is the flow of execution of an videocapture class api is executed in linux?

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How does the open(int index), set(), get(), etc.., api's in the VideoCapture Class gets executed in the Linux Operating System? I know what it does, i want to know how it is created, like for example open() api is implemented in the *cap_v4l.cpp *.

How does the flow of execution goes to that file and executes that api? Simply, How the flow of path of execution of the api is done in the linux operating system?