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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        Return value and action
     PF_INET     SOCK_DGRAM     IPPROTO_SCTP    Return -1.  The global
                                                variable 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
                                                variable 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 ALSO

     connect(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.