sendmsg.3.man

This a separate release of the OpenSS7 X/Open XTI/TLI library, TLI modules (timod, tirdwr) and the I

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.TH SENDMSG 3 "2004/05/16 02:35:35" "strxnet-0_9_2-4" "Linux Fast-STREAMS Sockets Library"
.SH NAME
.B sendmsg
\- send a message on a socket using a message structure
.SH SYNOPSIS
.PP
.B #include <sys/socket.h>
.HP
.BI "ssize_t sendmsg(int " socket ", const struct msghdr *" message ", int " flags );
.SH DESCRIPTION
.PP
The
.BR sendmsg ()
function sends a message through a connection-mode or
connectionless-mode socket.  If the socket is connectionless-mode, the message
will be sent to the address specified by
.BR msghdr .
If the socket is
connection-mode, the destination address in
.B msghdr
is ignored.
.PP
The function takes the following arguments:
.TP
.I socket
Specifies the socket file descriptor.
.TP
.I message
Points to a
.B msghdr
structure, containing both the destination address and the
buffers for the outgoing message.  The length and format of the address depend
on the address family of the socket.  The
.I msg_flags
member is ignored.
.TP
.I flags
Specifies the type of message transmission.  The application may specify 0 or
the following flag:
.RS
.TP
.B MSG_EOR
Terminates a record (if supported by the protocol)
.TP
.B MSG_OOB
Sends out-of-band data on sockets that support out-of-bound data.  The
significance and semantics of out-of-band data are protocol-specific.
.RE
.PP
The
.I msg_iov
and
.I msg_iovlen
fields of message specify zero or more buffers
containing the data to be sent.
.I msg_iov
points to an array of iovec
structures;
.I msg_iovlen
must be set to the dimension of this array.  In each
iovec structure, the
.I iov_base
field specifies a storage area and the
.I iov_len
field gives its size in bytes.  Some of these sizes can be zero.  The data from
each storage area indicated by
.I msg_iov
is sent in turn.
.PP
Successful completion of a call to
.BR sendmsg ()
does not guarantee delivery of
the message.  A return value of -1 indicates only locally-detected errors.
.PP
If space is not available at the sending socket to hold the message to be
transmitted and the socket file descriptor does not have
.B O_NONBLOCK
set,
.BR sendmsg ()
function blocks until space is available.  If space is not available
at the sending socket to hold the message to be transmitted and the socket
file descriptor does have
.B O_NONBLOCK
set,
.BR sendmsg ()
function will fail.
.PP
If the socket protocol supports broadcast and the specified address is a
broadcast address for the socket protocol,
.BR sendmsg ()
will fail if the
.B SO_BROADCAST
option is not set for the socket.
.PP
The socket in use may require the process to have appropriate privileges to
use the
.BR sendmsg ()
function.
.SH NOTES
.PP
The
.BR select (2)
and
.BR poll (2)
functions can be used to determine when it is
possible to send more data.
.SH CAVEATS
.PP
This system call is implemented as a
.B SIOCSOCKSYS
IOCTL.  See
.BR socksys (4)
for more information.
.SH "RETURN VALUE"
.PP
Upon successful completion,
.BR sendmsg ()
function returns the number of bytes
sent.  Otherwise, -1 is returned and errno is set to indicate the error.
.SH ERRORS
.PP
The
.BR sendmsg ()
function will fail if:
.TP
.RB [ EAGAIN "] or [" EWOULDBLOCK ]
The socket's file descriptor is marked
.B O_NONBLOCK
and the requested operation
would block.
.TP
.RB [ EAFNOSUPPORT ]
Addresses in the specified address family cannot be used with
this socket.
.TP
.RB [ EBADF ]
The socket argument is not a valid file descriptor.
.TP
.RB [ ECONNRESET ]
A connection was forcibly closed by a peer.
.TP
.RB [ EFAULT ]
The message parameter, or storage pointed to by the
.IR msg_name ,
.I msg_control
or
.I msg_iov
fields of the message parameter, or
storage pointed to by the iovec structures pointed to by the
.I msg_iov
field can not be accessed.
.TP
.RB [ EINTR ]
A signal interrupted
.BR sendmsg ()
before any data was transmitted.
.TP
.RB [ EINVAL ]
The sum of the
.I iov_len
values overflows an
.BR ssize_t .
.TP
.RB [ EMSGSIZE ]
The message is too large to be sent all at once (as the socket
requires), or the
.I msg_iovlen
member of the
.B msghdr
structure
pointed to by message is less than or equal to 0 or is greater
than {IOV_MAX}.
.TP
.RB [ ENOTCONN ]
The socket is connection-mode but is not connected.
.TP
.RB [ ENOTSOCK ]
The socket argument does not refer a socket.
.TP
.RB [ EOPNOTSUPP ]
The socket argument is associated with a socket that does not
support one or more of the values set in
.IR flags .
.TP
.RB [ EPIPE ]
The socket is shut down for writing, or the socket is
connection-mode and is no longer connected.  In the latter case,
and if the socket is of type
.BR SOCK_STREAM ,
the
.B SIGPIPE
signal is
generated to the calling process.
.PP
If the address family of the socket is
.BR AF_UNIX ,
then
.BR sendmsg ()
will
fail if:
.TP
.RB [ EIO ]
An I/O error occurred while reading from or writing to the file
system.
.TP
.RB [ ELOOP ]
Too many symbolic links were encountered in translating the
pathname in the socket address.
.TP
.RB [ ENAMETOOLONG ]
A component of a pathname exceeded
.RI { NAME_MAX }
characters, or an
entire pathname exceeded
.RI { PATH_MAX }
characters.
.TP
.RB [ ENOENT ]
A component of the pathname does not name an existing file or
the pathname is an empty string.
.TP
.RB [ ENOTDIR ]
A component of the path prefix of the pathname in the socket
address is not a directory.
.PP
The
.BR sendmsg ()
function may fail if:
.TP
.RB [ EACCES ]
Search permission is denied for a component of the path prefix;
or write access to the named socket is denied.
.TP
.RB [ EDESTADDRREQ ]
The socket is not connection-mode and does not have its peer
address set, and no destination address was specified.
.TP
.RB [ EHOSTUNREACH ]
The destination host cannot be reached (probably because the
host is down or a remote router cannot reach it).
.TP
.RB [ EIO ]
An I/O error occurred while reading from or writing to the file
system.
.TP
.RB [ EISCONN ]
A destination address was specified and the socket is already
connected.
.TP
.RB [ ENETDOWN ]
The local interface used to reach the destination is down.
.TP
.RB [ ENETUNREACH ]
No route to the network is present.
.TP
.RB [ ENOBUFS ]
Insufficient resources were available in the system to perform
the operation.
.TP
.RB [ ENOMEM ]
Insufficient memory was available to fulfill the request.
.TP
.RB [ ENOSR ]
There were insufficient
.IR STREAMS (4)
resources available for the
operation to complete.
.PP
If the address family of the socket is
.BR AF_UNIX ,
then
.BR sendmsg ()
may
fail if:
.TP
.RB [ ENAMETOOLONG ]
Pathname resolution of a symbolic link produced an intermediate
result whose length exceeds
.RI { PATH_MAX }.
.SH "SEE ALSO"
.PP
.BR getsockopt (3),
.BR poll (2),
.BR recv (3),
.BR recvfrom (3),
.BR recvmsg (3),
.BR select (2),
.BR send (3),
.BR sendto (3),
.BR setsockopt (3),
.BR shutdown (3),
.BR socket (3),
.BR <sys/socket.h> (5).
.SH "CONFORMING TO"
.PP
The Open Group XNS Issue 5.2.
.[
xns
.]
.\"
.\"
.[
$LIST$
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.TI