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.\" Copyright (c) 2007 Bruce M. Simpson.
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.\"     @(#)shutdown.2	8.1 (Berkeley) 6/4/93
.\" $FreeBSD: release/9.1.0/lib/libc/sys/shutdown.2 167292 2007-03-07 13:38:11Z bms $
.\"
.Dd March 5, 2007
.Dt SHUTDOWN 2
.Os
.Sh NAME
.Nm shutdown
.Nd disable sends and/or receives on a socket
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/types.h
.In 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.
The
.Fa how
argument specifies the type of shutdown.
Possible values are:
.Bl -tag -width ".Dv SHUT_RDWR"
.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; see
.Sx IMPLEMENTATION NOTES .
.It Dv SHUT_RDWR
Further sends and receives will be disallowed.
Implies
.Dv SHUT_WR .
.El
.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.
.\"
.Sh IMPLEMENTATION NOTES
The following protocol specific actions apply to the use of
.Dv SHUT_WR
(and potentially also
.Dv SHUT_RDWR ) ,
based on the properties of the socket associated with the file descriptor
.Fa s .
.Bl -column ".Dv PF_INET6" ".Dv SOCK_STREAM" ".Dv IPPROTO_SCTP"
.It Sy Domain Ta Sy Type Ta Sy Protocol Ta Sy Return value and action
.It Dv PF_INET Ta Dv SOCK_DGRAM Ta Dv IPPROTO_SCTP Ta
Return \-1.
The global variable
.Va errno
will be set to
.Er EOPNOTSUPP .
.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_SCTP Ta
Return 0.
Send queued data and tear down association.
.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_SCTP Ta
Return \-1.
The global variable
.Va errno
will be set to
.Er EOPNOTSUPP .
.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_SCTP Ta
Return 0.
Send queued data and tear down association.
.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 EOPNOTSUPP
The socket associated with the file descriptor
.Fa s
does not support this operation.
.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.
.El
.Sh SEE ALSO
.Xr connect 2 ,
.Xr socket 2 ,
.Xr inet 4 ,
.Xr inet6 4
.Sh STANDARDS
The
.Fn shutdown
system call is expected to comply with
.St -p1003.1g-2000 ,
when finalized.
.Sh HISTORY
The
.Fn shutdown
system call appeared in
.Bx 4.2 .
The
.Dv SHUT_RD , SHUT_WR ,
and
.Dv SHUT_RDWR
constants appeared in
.St -p1003.1g-2000 .
.Sh AUTHORS
.An -nosplit
This manual page was updated by
.An Bruce M. Simpson Aq bms@FreeBSD.org
to reflect how
.Fn shutdown
behaves with
.Dv PF_INET
and
.Dv PF_INET6
sockets.
.Sh BUGS
The ICMP
.Dq Li "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.