SHUTDOWN(2)               OpenBSD Programmer's Manual              SHUTDOWN(2)

NAME
     shutdown - disable sends or receives on a socket

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.

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

     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.

           SHUT_RDWR     Further sends and receives will be disallowed.

     The following protocol specific actions apply to the use of SHUT_WR 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_UDP    Return 0.  ICMP messages
                                                     will not be generated.
           PF_INET     SOCK_STREAM    IPPROTO_TCP    Return 0.  Send queued
                                                     data, wait for ACK, then
                                                     send FIN.
           PF_INET6    SOCK_DGRAM     IPPROTO_UDP    Return 0.  ICMP messages
                                                     will not be generated.
           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.

     [ENOTCONN]    The s argument specifies a SOCK_STREAM socket which is not
                   connected.

     [ENOTSOCK]    The s argument does not refer to a socket.

     [EOPNOTSUPP]  The socket associated with the file descriptor s does not
                   support this operation.

SEE ALSO
     connect(2), socket(2), inet(4), inet6(4)

HISTORY
     The shutdown() function call appeared in 4.2BSD.  The SHUT_RD, SHUT_WR,
     and SHUT_RDWR constants appeared in IEEE Std 1003.1g-2000 (``POSIX'').

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.

OpenBSD 4.9                      May 31, 2007                      OpenBSD 4.9