The
ioctl() function manipulates the underlying device parameters of special files. In particular, many operating characteristics of character special files (e.g. terminals) may be controlled with
ioctl() requests. The argument
d must be an open file descriptor.
An ioctl
request has encoded in it whether the argument is an “in” parameter or “out” parameter, and the size of the argument
argp in bytes. Macros and defines used in specifying an ioctl
request are located in the file <
sys/ioctl.h>.