The sendfilev() function attempts to write data from the sfvcnt buffers specified by the members of vec array: vec[0], vec[1], ... , vec[sfvcnt-1]. fildes is a file descriptor to a regular file or to a AF_NCA, AF_INET, or AF_INET6 family type SOCK_STREAM socket that is open for writing.

This function is analogous to the writev() system call. See writev(2). However, instead of sending out chunks of data, sendfilev() can read input data from data buffers or file descriptors.

The following is the sendfilevec structure:

typedef struct sendfilevec {
        int     sfv_fd;         /* input fd */
        uint_t  sfv_flag;       /* Flags. see below */
        off_t   sfv_off;        /* offset to start reading from */
        size_t  sfv_len;        /* amount of data */
} sendfilevec_t;

#define SFV_FD_SELF     (-2)

To send a file, open the file for reading. Point sfv_fd to the file descriptor returned as a result. See open(2). sfv_off should contain the offset within the file. sfv_len should have the length of the file to be transferred.

The xferred parameter is updated to record the total number of bytes written to out_fd.

The sfv_flag field is reserved and should be set to zero.

To send data directly from the address space of the process, set sfv_fd to SFV_FD_SELF. sfv_off should point to the data, with sfv_len containing the length of the buffer.

The sendfilev() function supports the following parameters:

fildes

A file descriptor to a regular file or to a AF_NCA, AF_INET, or AF_INET6 family type SOCK_STREAM socket that is open for writing. For AF_NCA, the protocol type should be zero.

vec

An array of SENDFILEVEC_T, as defined in the sendfilevec structure above.

sfvcnt

The number of members in vec.

xferred

The total number of bytes written to out_fd.

Upon successful completion, sendfilev() returns total number of bytes written to out_fd. Otherwise, it returns -1, and errno is set to indicate an error. xferred contains the amount of data successfuly transferred, which can be used to discover the error vector.

EAFNOSUPPORT

The implementation does not support the specified address family for socket.

EPROTOTYPE

The socket type is not supported.

EBADF

The fildes argument is not a valid descriptor open for writing or an sfv_fd is invalid or not open for reading.

EACCES

The process does not have appropriate privileges or one of the files pointed by sfv_fd does not have appropriate permissions.

EPIPE

The fildes argument is a socket that has been shut down for writing.

EIO

An I/O error occurred while accessing the file system.

EFAULT

The vec argument points to an illegal address.

EFAULT

The xferred argument points to an illegal address.

EINVAL

The sfvcnt argument was less than or equal to 0. One of the sfv_len in vec array was less than or equal to 0, or greater than the file size. An sfv_fd is not seekable.

EAGAIN

Mandatory file or record locking is set on either the file descriptor or output file descriptor if it points at regular files. O_NDELAY or O_NONBLOCK is set, and there is a blocking record lock. An attempt has been made to write to a stream that cannot accept data with the O_NDELAY or the O_NONBLOCK flag set.

The sendfilev() function has a transitional interface for 64-bit file offsets. See lf64(5).

The following example sends 2 vectors, one of HEADER data and a file of length 100 over sockfd. sockfd is in a connected state, that is, socket(), accept(), and bind() operation are complete.

#include <sys/sendfile.h>
.
.
.
int
main (int argc, char eargv[]){
  int sockfd;
  ssize_t ret;
  size_t xfer;
  struct sendfilevec vec[2];
    .
    .
    .
  vec[0].sfv_fd = SFV_FD_SELF;
  vec[0].sfv_flag = 0;
  vec[0].sfv_off = "HEADER_DATA";
  vec[0].sfv_len = strlen("HEADER_DATA");
  vec[1].sfv_fd = open("input_file",.... );
  vec[1].sfv_flag = 0;
  vec[1].sfv_off = 0;
  vec[1].sfv_len = 100;

  ret = sendfilev(sockfd, vec, 2, &xfer);
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.
.
}

See attributes(5) for descriptions of the following attributes:

open(2), writev(2), attributes(5)