SHUTDOWN(2) BSD System Calls Manual SHUTDOWN(2)NAMEshutdown — 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 spe‐
cific 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 asso‐
ciated with the file descriptor s.
Domain Type Protocol Return value and action
PF_INET SOCK_DGRAM IPPROTO_SCTP Return -1. The global vari‐
able errno will be set to
EOPNOTSUPP.
PF_INET SOCK_DGRAM IPPROTO_UDP Return 0. ICMP messages will
not be generated.
PF_INET SOCK_STREAM IPPROTO_SCTP Return 0. Send queued data
and tear down association.
PF_INET SOCK_STREAM IPPROTO_TCP Return 0. Send queued data,
wait for ACK, then send FIN.
PF_INET6 SOCK_DGRAM IPPROTO_SCTP Return -1. The global vari‐
able errno will be set to
EOPNOTSUPP.
PF_INET6 SOCK_DGRAM IPPROTO_UDP Return 0. ICMP messages will
not be generated.
PF_INET6 SOCK_STREAM IPPROTO_SCTP Return 0. Send queued data
and tear down association.
PF_INET6 SOCK_STREAM IPPROTO_TCP Return 0. 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.
[EOPNOTSUPP] The socket associated with the file descriptor s does
not support this operation.
[ENOTCONN] The s argument specifies a SOCK_STREAM socket which is
not connected.
[ENOTSOCK] The s argument does not refer to a socket.
SEE ALSOconnect(2), socket(2), inet(4), inet6(4)STANDARDS
The shutdown() system call is expected to comply with IEEE Std
1003.1g-2000 (“POSIX.1”), 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.1”).
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.
BSD March 5, 2007 BSD
