The ioctls listed in this manual page apply directly to sockets, independent of any underlying protocol. The setsockopt() call (see getsockopt(3SOCKET)) is the primary method for operating on sockets, rather than on the underlying
protocol or network interface. ioctls for a specific network interface or protocol are documented in the manual page for that interface or protocol.
SIOCSPGRP
The argument is a pointer to an int. Set the
process-group ID that will subsequently receive SIGIO or SIGURG signals for the socket
referred to by the descriptor passed to ioctl to the value of that int. The argument must be either positive (in which case it must be a process ID) or negative (in which case it must be a process group).
SIOCGPGRP
The argument is a pointer to an int. Set the value of that int
to the process-group ID that is receiving SIGIO or SIGURG signals for the socket referred
to by the descriptor passed to ioctl.
SIOCCATMARK
The argument is a pointer to an int. Set the value of that int
to 1 if the read pointer for the socket referred to by the descriptor passed to ioctl points to a mark in the data stream for an out-of-band message. Set the value
of that int to 0 if the read pointer for the socket referred to by the descriptor passed to ioctl does not point to a mark in the data stream for
an out-of-band message.
