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IOCTL(2) System Calls Manual IOCTL(2) NAME ioctl - miscellaneous control operations SYNOPSIS #include <sys/filio.h> int ioctl(fildes, request, param) void *param; DESCRIPTION Ioctl performs a variety of requests on open files, most applying only to particular device files. The writeups of various devices in section 4 discuss how ioctl applies to them; see stream(4) in particular for operations applying to communication devices. Param points to a parameter buffer. Some requests read data from the buffer; others write data to the buffer; some do both. The buffer's size varies according to the request. A few provide meaningful data in the return value from ioctl as well; others return a conventional value of 0 for success, -1 for failure. Requests for different drivers are defined in different header files. Two standard calls, defined in <sys/filio.h>, apply to any open file: ioctl(fildes, FIOCLEX, (void *)0); ioctl(fildes, FIONCLEX, (void *)0); The first causes the file to be closed automatically upon a successful exec(2); the second causes the file to be left open. SEE ALSO exec(2), stream(4) DIAGNOSTICS EBADF, EFAULT, EIO, ENODEV, ENOTTY BUGS Ioctl requests vary among UNIX systems; undisciplined use is likely to compromise portability. The size of the parameter buffer should be an explicit argument. IOCTL(2)