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sendmsg()

Send a message and its header to a socket

Synopsis:

#include <sys/types.h>
#include <sys/socket.h>

ssize_t sendmsg( int s,
                 const struct msghdr * msg,
                 int flags );

Arguments:

s
The descriptor for the socket; see socket().
msg
A pointer to the message that you want to send. For a description of the msghdr structure, see recvmsg().
flags
A combination of the following:

Library:

libsocket

Use the -l socket option to qcc to link against this library.

Description:

The sendmsg() function is used to transmit a message to another socket. You can use send() only when the socket is in a connected state; you can use sendmsg() at any time.

No indication of failure to deliver is implicit in a sendmsg(). Locally detected errors are indicated by a return value of -1.

If no message space is available at the socket to hold the message to be transmitted, then sendmsg() normally blocks, unless the socket has been placed in nonblocking I/O mode. You can use select() to determine when it's possible to send more data.

Returns:

The number of bytes sent, or -1 if an error occurs (errno is set).

Errors:

EBADF
An invalid descriptor was specified.
EDESTADDRREQ
A destination address is required.
EFAULT
An invalid user space address was specified for a parameter.
EMSGSIZE
The socket requires that the message be sent atomically, but the size of the message made this impossible.
ENOBUFS
The system couldn't allocate an internal buffer. The operation may succeed when buffers become available.
ENOTSOCK
The argument s isn't a socket.
EWOULDBLOCK
The socket is marked nonblocking and the requested operation would block.

Classification:

POSIX 1003.1

Safety:
Cancellation point Yes
Interrupt handler No
Signal handler No
Thread Yes

See also:

getsockopt(), ioctl(), recv(), select(), send(), sendto(), socket(), write()