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  man pages->IRIX man pages -> standard/recv (2)              


RECV(2)								       RECV(2)

NAME    [Toc]    [Back]

     recv, recvfrom, recvmsg - receive a message from a	socket

SYNOPSIS    [Toc]    [Back]

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

     int recv(int s, void *buf,	int len, int flags);

     int recvfrom(int s, void *buf, int	len, int flags,
	       struct sockaddr *from, int *fromlen);
     int recvmsg(int s,	struct msghdr *msg, int	flags);

DESCRIPTION    [Toc]    [Back]

     Recv, recvfrom, and recvmsg are used to receive messages from a socket.

     The recv call is normally used only on a connected	socket (see
     connect(2)), while	recvfrom and recvmsg may be used to receive data on a
     socket whether it is in a connected state or not.

     If	from is	non-zero, the source address of	the message is filled in.
     Fromlen is	a value-result parameter, initialized to the size of the
     buffer associated with from, and modified on return to indicate the
     actual size of the	address	stored there.  A successful call returns the
     length of the message.  If	a message is too long to fit in	the supplied
     buffer, excess bytes may be discarded depending on	the type of socket the
     message is	received from (see socket(2)).

     If	no messages are	available at the socket, the receive call waits	for a
     message to	arrive,	unless the socket is nonblocking (see ioctl(2))	in
     which case	the call returns -1 with the external variable errno set to

     The select(2) call	may be used to determine when more data	arrives.

     The flags argument	to a recv call is formed by or'ing one or more of the

       #define MSG_OOB	    0x1	 /* process out-of-band	data */
       #define MSG_PEEK	    0x2	 /* peek at incoming message */
       #define MSG_WAITALL  0x40 /* wait for full request or error */
       #define MSG_DONTWAIT 0x80 /* this message should	be nonblocking */

     The recvmsg call uses a msghdr structure to minimize the number of
     directly supplied parameters.  This structure has the following form, as
     defined in	<sys/socket.h>:

	  struct msghdr	{
	       caddr_t	 msg_name; /* optional address */
	       int  msg_namelen;   /* size of address */
	       struct	 iovec *msg_iov;     /*	scatter/gather array */
	       int  msg_iovlen;	   /* #	elements in msg_iov */

									Page 1

RECV(2)								       RECV(2)

	      caddr_t	 msg_accrights;	/* access rights sent/received */
	       int  msg_accrightslen;

     Here msg_name and msg_namelen specify the destination address if the
     socket is unconnected; msg_name may be given as a null pointer if no
     names are desired or required.  The msg_iov and msg_iovlen	describe the
     scatter/gather locations.	The iovec structure is defined as

	  struct iovec {
	       caddr_t	 iov_base;
	       int  iov_len;

     Each iovec	entry specifies	the base address and length of an area in
     memory where data should be placed. recvmsg will always fill an area
     completely	before proceeding to the next.

     A buffer to receive any access rights sent	along with the message is
     specified in msg_accrights, which has length msg_accrightslen.  Access
     rights are	opaque data that are interpreted within	the context of the
     communication domain and are currently limited to file descriptors, which
     each occupy the size of an	int (see unix(7F) for details).

RETURN VALUE    [Toc]    [Back]

     These calls return	the number of bytes received, or -1 if an error

ERRORS    [Toc]    [Back]

     The calls fail if:

     [EBADF]		 The argument s	is an invalid descriptor.

     [ENOTSOCK]		 The argument s	is not a socket.

     [EWOULDBLOCK]	 The socket is marked non-blocking and the receive
			 operation would block.

     [EINTR]		 The receive was interrupted by	delivery of a signal
			 before	any data was available for the receive.

     [EFAULT]		 The data was specified	to be received into a nonexistent
 or protected part of the process address

SEE ALSO    [Toc]    [Back]

     fcntl(2), getsockopt(2), read(2), select(2), send(2), socket(2)

NOTES    [Toc]    [Back]

     ABI-compliant versions of the above calls can be obtained from

									Page 2

RECV(2)								       RECV(2)

     When using	recvmsg	to receive access rights, it may be necessary for the
     application to request a single byte of normal data as well, so that the
     call does not return immediately if the access rights are not yet
     present.  Doing so	will cause the recvmsg call to block until the access
     rights are	available.

									PPPPaaaaggggeeee 3333
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