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    The following form allows you to view linux man pages.

    Command:

    sendmmsg

    
    
    

    SYNOPSIS

           #define _GNU_SOURCE
           #include <sys/socket.h>
    
           int sendmmsg(int sockfd, struct mmsghdr *msgvec, unsigned int vlen,
                        unsigned int flags);
    
    
    

    DESCRIPTION

           The  sendmmsg()  system  call is an extension of sendmsg(2) that allows
           the caller to transmit multiple messages on a  socket  using  a  single
           system call.  (This has performance benefits for some applications.)
    
           The  sockfd argument is the file descriptor of the socket on which data
           is to be transmitted.
    
           The msgvec argument is a pointer to an  array  of  mmsghdr  structures.
           The size of this array is specified in vlen.
    
           The mmsghdr structure is defined in <sys/socket.h> as:
    
               struct mmsghdr {
                   struct msghdr msg_hdr;  /* Message header */
                   unsigned int  msg_len;  /* Number of bytes transmitted */
               };
    
           The  msg_hdr  field  is a msghdr structure, as described in sendmsg(2).
           The msg_len field is used to return the number of bytes sent  from  the
           message  in  msg_hdr  (i.e., the same as the return value from a single
           sendmsg(2) call).
    
           The flags argument contains flags ORed together.   The  flags  are  the
           same as for sendmsg(2).
    
           A  blocking  sendmmsg() call blocks until vlen messages have been sent.
           A nonblocking call sends as many messages as possible (up to the  limit
           specified by vlen) and returns immediately.
    
           On return from sendmmsg(), the msg_len fields of successive elements of
           msgvec are updated to contain the number of bytes transmitted from  the
           corresponding msg_hdr.  The return value of the call indicates the num-
           ber of elements of msgvec that have been updated.
    
    
    

    RETURN VALUE

           On success, sendmmsg() returns the number of messages sent from msgvec;
           if  this  is  less than vlen, the caller can retry with a further send-
           mmsg() call to send the remaining messages.
    
           On error, -1 is returned, and errno is set to indicate the error.
    
    
    

    ERRORS

           Errors are as for sendmsg(2).  An error is returned only  if  no  data-
           grams could be sent.
           datagram originates from a pair of buffers.
    
           #define _GNU_SOURCE
           #include <netinet/ip.h>
           #include <stdio.h>
           #include <stdlib.h>
           #include <string.h>
           #include <sys/types.h>
           #include <sys/socket.h>
    
           int
           main(void)
           {
               int sockfd;
               struct sockaddr_in sa;
               struct mmsghdr msg[2];
               struct iovec msg1[2], msg2;
               int retval;
    
               sockfd = socket(AF_INET, SOCK_DGRAM, 0);
               if (sockfd == -1) {
                   perror("socket()");
                   exit(EXIT_FAILURE);
               }
    
               sa.sin_family = AF_INET;
               sa.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
               sa.sin_port = htons(1234);
               if (connect(sockfd, (struct sockaddr *) &sa, sizeof(sa)) == -1) {
                   perror("connect()");
                   exit(EXIT_FAILURE);
               }
    
               memset(msg1, 0, sizeof(msg1));
               msg1[0].iov_base = "one";
               msg1[0].iov_len = 3;
               msg1[1].iov_base = "two";
               msg1[1].iov_len = 3;
    
               memset(&msg2, 0, sizeof(msg2));
               msg2.iov_base = "three";
               msg2.iov_len = 5;
    
               memset(msg, 0, sizeof(msg));
               msg[0].msg_hdr.msg_iov = msg1;
               msg[0].msg_hdr.msg_iovlen = 2;
    
               msg[1].msg_hdr.msg_iov = &msg2;
               msg[1].msg_hdr.msg_iovlen = 1;
    
               retval = sendmmsg(sockfd, msg, 2, 0);
               if (retval == -1)
    
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