Benzene is a widely used industrial chemical. Benzene is found in crude oil and is a major part of gasoline. Its used to make plastics, resins, synthetic fibers, rubber lubricants, dyes, detergents, drugs and pesticides. Benzene is produced naturally by volcanoes and forest fires. In homes, benzene may be found in glues, adhesives, cleaning products, paint strippers, tobacco smoke and gasoline.
A system call is an interface between a user-space application and a service that the kernel provides. Because the service is provided in the kernel, a direct call cannot be performed; instead, you must use a process of crossing the user-space/kernel boundary.
9.2.3 Calling User-Defined Functions. Calling a function means causing the function to run and do its job. A function call is an expression and its value is the value returned by the function. A function call consists of the function name followed by the arguments in parentheses. awk expressions are what you write in the call for the arguments.