NAME

shutdown —

disable sends and/or receives on a socket

LIBRARY

Standard C Library (libc, -lc)

SYNOPSIS

#include <sys/types.h>
#include <sys/socket.h>

int
shutdown(int s, int how);

DESCRIPTION

The shutdown() system call disables sends or receives on a socket. The how argument specifies the type of shutdown. Possible values are:

SHUT_RD: Further receives will be disallowed.
SHUT_WR: Further sends will be disallowed. This may cause actions specific to the protocol family of the socket s to happen; see IMPLEMENTATION NOTES.
SHUT_RDWR: Further sends and receives will be disallowed. Implies SHUT_WR.

If the file descriptor s is associated with a SOCK_STREAM socket, all or part of the full-duplex connection will be shut down.

IMPLEMENTATION NOTES

The following protocol specific actions apply to the use of SHUT_WR (and potentially also SHUT_RDWR), based on the properties of the socket associated with the file descriptor s.

Domain	Type	Protocol	Action
`PF_INET`	`SOCK_DGRAM`	`IPPROTO_SCTP`	Failure, as socket is not connected.
`PF_INET`	`SOCK_DGRAM`	`IPPROTO_UDP`	Failure, as socket is not connected.
`PF_INET`	`SOCK_STREAM`	`IPPROTO_SCTP`	Send queued data and tear down association.
`PF_INET`	`SOCK_STREAM`	`IPPROTO_TCP`	Send queued data, wait for ACK, then send FIN.
`PF_INET6`	`SOCK_DGRAM`	`IPPROTO_SCTP`	Failure, as socket is not connected.
`PF_INET6`	`SOCK_DGRAM`	`IPPROTO_UDP`	Failure, as socket is not connected.
`PF_INET6`	`SOCK_STREAM`	`IPPROTO_SCTP`	Send queued data and tear down association.
`PF_INET6`	`SOCK_STREAM`	`IPPROTO_TCP`	Send queued data, wait for ACK, then send FIN.

RETURN VALUES

The shutdown() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.

ERRORS

The shutdown() system call fails if:

[EBADF]: The s argument is not a valid file descriptor.
[EINVAL]: The how argument is invalid.
[ENOTCONN]: The s argument specifies a socket which is not connected.
[ENOTSOCK]: The s argument does not refer to a socket.

STANDARDS

The shutdown() system call is expected to comply with IEEE Std 1003.1g-2000 (“POSIX.1g”), when finalized.

HISTORY

The shutdown() system call appeared in 4.2BSD. The SHUT_RD, SHUT_WR, and SHUT_RDWR constants appeared in IEEE Std 1003.1g-2000 (“POSIX.1g”).

AUTHORS

This manual page was updated by Bruce M. Simpson <bms@FreeBSD.org> to reflect how shutdown() behaves with PF_INET and PF_INET6 sockets.

BUGS

The ICMP “port unreachable” message should be generated in response to datagrams received on a local port to which s is bound after shutdown() is called.