The default error behavior of the primitive procedures defined by
the UNIX extension is to invoke the standard Scheme
error handler if a UNIX system call or library function fails.
As an alternative, if a specific error action is to be performed
by the application, a primitive procedure can be invoked under
control of the
In this case, a unique
error object is returned if a UNIX function signals an error.
The standard UNIX system error message and the UNIX error number
are made available to the application in any case.
Details of the error handling facilities are described in the
section ``Error Functions'' below.