.\"	$OpenBSD: shutdown.2,v 1.14 2013/07/17 05:42:11 schwarze Exp $
.\"	$NetBSD: shutdown.2,v 1.5 1995/02/27 12:37:11 cgd Exp $
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.\"     @(#)shutdown.2	8.1 (Berkeley) 6/4/93
.\"
.Dd $Mdocdate: July 17 2013 $
.Dt SHUTDOWN 2
.Os
.Sh NAME
.Nm shutdown
.Nd disable sends or receives on a socket
.Sh SYNOPSIS
.Fd #include <sys/socket.h>
.Ft int
.Fn shutdown "int s" "int how"
.Sh DESCRIPTION
The
.Fn shutdown
system call disables sends or receives on a socket.
.Pp
If the file descriptor
.Fa s
is associated with a
.Dv SOCK_STREAM
socket, all or part of the full-duplex connection will be shut down.
.Pp
The
.Fa how
argument specifies the type of shutdown.
Possible values are:
.Bl -tag -width "SHUT_RDWRXXX" -offset indent
.It Dv SHUT_RD
Further receives will be disallowed.
.It Dv SHUT_WR
Further sends will be disallowed.
This may cause actions specific to the protocol family of the socket
.Fa s
to happen.
.It Dv SHUT_RDWR
Further sends and receives will be disallowed.
.El
.Pp
The following protocol specific actions apply to the use of
.Dv SHUT_WR
based on the properties of the socket associated with the file descriptor
.Fa s :
.Bl -column "PF_INET6" "SOCK_STREAM" "IPPROTO_UDP" -offset indent
.It DOMAIN Ta TYPE Ta PROTOCOL Ta "RETURN VALUE AND ACTION"
.Pp
.It Dv PF_INET Ta Dv SOCK_DGRAM Ta Dv IPPROTO_UDP Ta
Return 0.
ICMP messages will
.Em not
be generated.
.It Dv PF_INET Ta Dv SOCK_STREAM Ta Dv IPPROTO_TCP Ta
Return 0.
Send queued data, wait for ACK, then send FIN.
.It Dv PF_INET6 Ta Dv SOCK_DGRAM Ta Dv IPPROTO_UDP Ta
Return 0.
ICMP messages will
.Em not
be generated.
.It Dv PF_INET6 Ta Dv SOCK_STREAM Ta Dv IPPROTO_TCP Ta
Return 0.
Send queued data, wait for ACK, then send FIN.
.El
.Sh RETURN VALUES
.Rv -std shutdown
.Sh ERRORS
The
.Fn shutdown
system call fails if:
.Bl -tag -width Er
.It Bq Er EBADF
The
.Fa s
argument is not a valid file descriptor.
.It Bq Er EINVAL
The
.Fa how
argument is invalid.
.It Bq Er ENOTCONN
The
.Fa s
argument specifies a
.Dv SOCK_STREAM
socket which is not connected.
.It Bq Er ENOTSOCK
The
.Fa s
argument does not refer to a socket.
.It Bq Er EOPNOTSUPP
The socket associated with the file descriptor
.Fa s
does not support this operation.
.El
.Sh SEE ALSO
.Xr connect 2 ,
.Xr socket 2 ,
.Xr inet 4 ,
.Xr inet6 4
.Sh STANDARDS
The
.Fn shutdown
function conforms to
.St -p1003.1-2008 .
.Sh HISTORY
The
.Fn shutdown
system call first appeared in
.Bx 4.1c .
The
.Dv SHUT_RD , SHUT_WR ,
and
.Dv SHUT_RDWR
constants appeared in
.St -p1003.1g-2000 .
.Sh BUGS
The ICMP
.Dq port unreachable
message should be generated in response to
datagrams received on a local port to which
.Fa s
is bound
after
.Fn shutdown
is called.